Refrigerant suction structure in fixed displacement type piston compressor, and operation control method in fixed displacement type piston compressor

ABSTRACT

An introduction passage of rotary valve has outlets for feeding out refrigerant in a suction pressure zone toward each of compression chambers. A switch portion in a shutoff state shuts off a portion of the suction pressure zone within a compressor from the outlets of the introduction passage. The switch portion includes a valve body, a working pressure chamber, and a working pressure applying portion. The working pressure chamber introduces a working pressure that is applied to the valve body so as to arrange the valve body at a communication position. The pressure in the suction pressure zone acts against the pressure in the working pressure chamber through the valve body.

BACKGROUND OF THE INVENTION

The present invention relates to a refrigerant suction structure in afixed displacement type piston compressor provided with a rotary valve.The piston defines a compression chamber within a cylinder bore. Therotary valve has an introduction passage for introducing refrigerantfrom a suction pressure zone to the compression chamber. The rotaryvalve integrally rotates with a rotary shaft. Further, the presentinvention relates to an operation control method in the fixeddisplacement type piston compressor.

Japanese Laid-Open Patent Publication Nos. 7-119631 and 2006-83835 eachdisclose a piston compressor using a rotary valve. Japanese Laid-OpenPatent Publication Nos. 64-88064 and 2000-145629 each disclose a pistoncompressor using a reed valve type suction valve. The piston compressorusing the rotary valve has a less suction resistance at a time ofdrawing suction gas into a cylinder bore and is excellent in an energyefficiency in comparison with the piston compressor using the reed typesuction valve.

Japanese Laid-Open Patent Publication No. 7-119631 discloses a startingimpact which may be generated at a time of starting a compressor. Iftorque is rapidly increased in accordance with compression of gas at atime of starting the compressor, a load is applied to an internalcombustion engine, which serves as a vehicle engine. As a result, atraveling speed of the vehicle may be lowered for a moment. In thiscase, a vehicle occupant feels a shock.

The rotary valve in Japanese Laid-Open Patent Publication No. 7-119631can be moved in an axial direction of a rotary shaft in correspondenceto a pressure in a control pressure chamber. The compressor has asuction port, which is a suction pressure zone positioned in a centerportion of a cylinder block. The rotary valve has a bypass groove whichcan connect the cylinder bore with the suction port. The rotary valve ismoved in the axial direction in such a manner that the bypass grooveconnects almost all the cylinder bores with the suction port at a timewhen the operation of the compressor is stopped and when the compressoris started. Accordingly, even if the piston actuates so as to compressthe gas within the cylinder bore at a time of starting the compressor,the gas within the cylinder bore flows to the suction port via thebypass groove. As a result, the starting impact is suppressed.

It is necessary to minimize a clearance in a peripheral surface of therotary valve, so that the gas does not leak along a peripheral surfaceof the rotary valve, and that the rotary valve can be rotated. Further,it is necessary that the clearance allows the rotary valve to move inthe axial direction. However, it is very difficult to control theclearance mentioned above.

The piston compressor in Japanese Laid-Open Patent Publication No.2000-145629 has a differential pressure sensitive on-off valve which isopened and closed on the basis of a differential pressure between adischarge pressure and a suction pressure. The differential pressuresensitive on-off valve is arranged between a low pressure refrigerantconduit introducing the refrigerant to the compressor from the outsideof the compressor, and a suction chamber positioned within thecompressor. If the compressor is started from a pressure balanced state,the differential pressure sensitive on-off valve comes to a closedstate, and stops an inflow of the refrigerant from the outside of thecompressor to the suction chamber. As a result, the starting impact isreduced.

However, even if the differential pressure sensitive on-off valve comesto the closed state, the refrigerant is left in the suction chamber, andthe residual refrigerant is drawn to the cylinder bore so as to becompressed. Since the volumetric capacity of the suction chamber islarge so as to suppress a suction pulsation of the compressor, theamount of the refrigerant drawn into the cylinder bore in a state inwhich the differential pressure sensitive on-off valve is closed islarge. Accordingly, the effect of reducing the starting impact obtainedby the differential pressure sensitive on-off valve is not sufficient.

SUMMARY OF THE INVENTION

An objective of the present invention is to improve the effect ofreducing the starting impact.

According to one aspect of the invention, a refrigerant suctionstructure in a fixed displacement type piston compressor is provided.The compressor includes a rotary shaft coupled to an external drivesource via a clutch. A plurality of cylinder bores are arranged aroundthe rotary shaft. A plurality of pistons define compression chambers inthe cylinder bores by being respectively accommodated in the cylinderbores. A cam body is integrated with the rotary shaft. The cam bodyconverts a rotation of the rotary shaft into reciprocation of each ofthe pistons. A rotary valve has an introduction passage for introducinga refrigerant from a suction pressure zone to each of the compressionchambers. The rotary valve integrally rotates with the rotary shaft. Thesuction pressure zone has a portion within the compressor. Theintroduction passage has outlets for feeding out the refrigerant towardeach of the compression chambers. The refrigerant suction structure hasa switch portion capable of being switched between a communication stateand a shutoff state. The switch portion in the communication stateallows the portion of the suction pressure zone within the compressor tocommunicate with the outlets of the introduction passage. The switchportion in the shutoff state shuts off the portion of the suctionpressure zone within the compressor from the outlets of the introductionpassage. The switch portion includes a valve body, a working pressurechamber, and a working pressure applying portion. The valve body iscapable of being switched between a communication position and a shutoffposition. The valve body in the communication position allows theportion of the suction pressure zone within the compressor tocommunicate with the outlets of the introduction passage. The valve bodyin the shutoff position shuts off the portion of the suction pressurezone within the compressor from the outlets of the introduction passage.The working pressure chamber introduces a working pressure that isapplied to the valve body so as to arrange the valve body at thecommunication position. The working pressure applying portion appliesthe working pressure to the working pressure chamber. The pressure inthe suction pressure zone acts against the pressure in the workingpressure chamber through the valve body.

Further, according to another aspect of the invention, a refrigerantsuction structure in a fixed displacement type piston compressor isprovided. The refrigerant suction structure has a switch portion capableof being switched between a communication state and a shutoff state. Theswitch portion in the communication state allows the portion of thesuction pressure zone within the compressor to communicate with theoutlets of the introduction passage. The switch portion in the shutoffstate shuts off the portion of the suction pressure zone within thecompressor from the outlets of the introduction passage. The switchportion includes a valve body capable of being switched between acommunication position and a shutoff position. The valve body in thecommunication position allows the portion of the suction pressure zonewithin the compressor to communicate with the outlets of theintroduction passage. The valve body in the shutoff position shuts offthe portion of the suction pressure zone within the compressor from theoutlets of the introduction passage. An electromagnetic driving portiondrives the valve body on the basis of an electromagnetic force.

Further, another aspect of the invention, an operation control method ina fixed displacement type piston compressor is provided. The operationcontrol method includes preparing a switch portion capable of beingswitched between a communication state and a shutoff state. The switchportion in the communication state allows the portion of the suctionpressure zone within the compressor to communicate with the outlets ofthe introduction passage. The switch portion in the shutoff state shutsoff the portion of the suction pressure zone within the compressor fromthe outlets of the introduction passage. The switch portion is providedwith a valve body, a working pressure chamber, and a working pressureapplying portion. The valve body is capable being switched between acommunication position allowing the portion of the suction pressure zonewithin the compressor to communicate with the outlet of the introductionpassage, and a shutoff position shutting off the portion of the suctionpressure zone within the compressor from the outlets of the introductionpassage. The working pressure chamber introduces a working pressureapplied to the valve body to arrange the valve body at the communicationposition. The working pressure applying portion applies the workingpressure to the working pressure chamber. The working pressure applyingportion is provided with a switch valve that is switched between a firststate, in which the refrigerant in the discharge pressure zone can befed to the working pressure chamber and a second state, in which therefrigerant in the discharge pressure chamber cannot be fed to theworking pressure chamber. The operation control method further includessetting the clutch to a coupled state after setting the switch valve tothe second state, at a time of switching the clutch from the shutoffstate to the coupled state. The operation control method furtherincludes switching the switch valve to the first state after setting theclutch to the coupled state.

Further, according to another aspect of the invention, an operationcontrol method in a fixed displacement type piston compressor isprovided. The operation control method includes preparing a switchportion capable of being switched between a communication state and ashutoff state. The switch portion in the communication state allows theportion of the suction pressure zone within the compressor tocommunicate with the outlets of the introduction passage. The switchportion in the shutoff state shuts off the portion of the suctionpressure zone within the compressor from the outlets of the introductionpassage. The switch portion is provided with a valve body and anelectromagnetic driving portion. The valve body is capable beingswitched between a communication position allowing the portion of thesuction pressure zone within the compressor to communicate with theoutlets of the introduction passage, and a shutoff position shutting offthe portion of the suction pressure zone within the compressor from theoutlets of the introduction passage. The electromagnetic driving portionis capable of driving the valve body on the basis of an electromagneticforce. The electromagnetic driving portion is capable of switching thevalve body between a first state, in which the valve body is arranged atthe communication position, and a second state, in which the valve bodyis arranged at the shutoff position. The operation control methodfurther includes setting the clutch to the coupled state after settingthe electromagnetic driving portion to the second state, at a time ofswitching the clutch from the shutoff state to the coupled state. Theoperation control method further includes setting the electromagneticdriving portion to the first state after setting the clutch to thecoupled state.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel areset forth with particularity in the appended claims. The invention,together with objects and advantages thereof, may best be understood byreference to the following description of the presently preferredembodiments together with the accompanying drawings in which:

FIG. 1 is a side cross-sectional view of a whole of a compressor,showing a first embodiment;

FIG. 2A is a cross-sectional view taken along line 2A-2A in FIG. 1;

FIG. 2B is a cross-sectional view taken along line 2B-2B in FIG. 1;

FIG. 3 is a partial enlarged view of FIG. 1;

FIG. 4 is an enlarged view showing a state in which the valve body ismoved from the position shown in FIG. 3;

FIG. 5 is a flowchart showing an operation control program of thecompressor in FIG. 1;

FIG. 6 is a timing chart showing a torque fluctuation in accordance witha program in FIG. 5;

FIG. 7 is a timing chart showing a second embodiment;

FIG. 8 is a side cross-sectional view of a whole of a compressor inaccordance with a third embodiment;

FIG. 9A is a partial enlarged view showing a state in which theelectromagnetic valve is switched from the state shown in FIG. 8;

FIG. 9B is a timing chart of the compressor in FIG. 8;

FIG. 10 is a partial enlarged side cross-sectional view of a compressorin accordance with a fourth embodiment;

FIG. 11A is a cross-sectional view showing a state in which theelectromagnetic valve is switched from the state shown in FIG. 10;

FIG. 11B is a timing chart of the compressor in FIG. 10;

FIG. 12A is a partial enlarged side cross-sectional view of a compressorin accordance with a fifth embodiment;

FIG. 12B is a cross-sectional view showing a state in which theelectromagnetic valve is switched from the state shown in FIG. 12A;

FIG. 13 is a side cross-sectional view of a whole of a compressor inaccordance with a sixth embodiment;

FIG. 14 is a cross-sectional view showing a state in which theelectromagnetic valve is switched from the state shown in FIG. 13;

FIG. 15A is a partial enlarged side cross-sectional view of a compressorin accordance with a seventh embodiment;

FIG. 15B is a cross-sectional view showing a state in which the valvebody is moved from the position shown in FIG. 15A;

FIG. 16A is a partial enlarged side cross-sectional view of a compressorin accordance with an eighth embodiment;

FIG. 16B is a cross-sectional view showing a state in which the valvebody is moved from the position shown in FIG. 16A;

FIG. 17 is a side cross-sectional view of a whole of a compressor inaccordance with a ninth embodiment;

FIG. 18A is a partial enlarged view of FIG. 17;

FIG. 18B is a cross-sectional view showing a state in which the valvebody is moved from the position shown in FIG. 18A;

FIG. 19A is a partial enlarged side cross-sectional view of a compressorin accordance with a tenth embodiment;

FIG. 19B is a cross-sectional view showing a state in which theelectromagnetic valve is switched from the state shown in FIG. 19A;

FIG. 20 is a side cross-sectional view of a whole of a one-headed pistoncompressor in accordance with an eleventh embodiment;

FIG. 21 is a side cross-sectional view of a whole of a compressor inaccordance with a twelfth embodiment;

FIG. 22A is a cross-sectional view taken along line 22A-22A in FIG. 21;

FIG. 22B is a cross-sectional view taken along line 22B-22B in FIG. 21;

FIG. 23 is a partial enlarged cross-sectional view of FIG. 21;

FIG. 24 is an enlarged view showing a state in which the valve body ismoved from the position shown in FIG. 23;

FIG. 25 is a flowchart showing an operation control program of thecompressor in FIG. 21;

FIG. 26 is a timing chart showing a torque fluctuation in accordancewith a program in FIG. 25;

FIG. 27 is a timing chart showing a thirteenth embodiment;

FIG. 28A is a partial enlarged cross-sectional view of a compressor inaccordance with a fourteenth embodiment;

FIG. 28B is a cross-sectional view showing a state in which the valvebody is moved from the position shown in FIG. 28A;

FIG. 29A is a partial enlarged cross-sectional view of a compressor inaccordance with a fifteenth embodiment;

FIG. 29B is a cross-sectional view showing a state in which the valvebody is moved from the position shown in FIG. 29A;

FIG. 30A is a partial enlarged cross-sectional view of a compressor inaccordance with a sixteenth embodiment;

FIG. 30B is a cross-sectional view showing a state in which the valvebody is moved from the position shown in FIG. 30A;

FIG. 31A is a partial enlarged side cross-sectional view of a compressorin accordance with a seventeenth embodiment;

FIG. 31B is a cross-sectional view showing a state in which the valvebody is moved from the position shown in FIG. 31A;

FIG. 32A is a partial enlarged side cross-sectional view of a compressorin accordance with an eighteenth embodiment;

FIG. 32B is a cross-sectional view showing a state in which the valvebody is moved from the position shown in FIG. 32A;

FIG. 33A is a partial enlarged side cross-sectional view of a compressorin accordance with a nineteenth embodiment;

FIG. 33B is a cross-sectional view showing a state in which the valvebody is moved from the position shown in FIG. 33A; and

FIG. 34 is a side cross-sectional view of a whole of a compressor inaccordance with a twentieth embodiment.

DETAILED DESCRIPTION OF PREFERABLE EMBODIMENTS

FIGS. 1 to 6 show a fixed displacement type piston compressor 10 inaccordance with a first embodiment obtained by embodying the presentinvention.

As shown in FIG. 1, a front cylinder block 11 is coupled to a rearcylinder block 12. A front housing member 13 is coupled to the frontcylinder block 11, and a rear housing member 14 is coupled to the rearcylinder block 12. The front cylinder block 11, the rear cylinder block12, the front housing member 13 and the rear housing member 14 constructa whole housing of the compressor 10.

A front discharge chamber 131 is formed in the front housing member 13.A rear discharge chamber 141 and a suction chamber 142 are formed in therear housing member 14. Each of the front discharge chamber 131 and therear discharge chamber 141 is a portion of a discharge pressure zonewithin the compressor 10. The suction chamber 142 is a portion of asuction pressure zone within the compressor 10. The inside of thecompressor refers to the inside of the entire housing of the compressor10, and the outside of the compressor refers to the outside of theentire housing of the compressor 10.

As shown in FIG. 1, a valve plate 15, a valve forming plate 16, and aretainer forming plate 17 are arranged between the front cylinder block11 and the front housing member 13. A valve plate 18, a valve formingplate 19, and a retainer forming plate 20 are formed between the rearcylinder block 12 and the rear housing member 14. Discharge ports 151and 181 are formed respectively in the valve plates 15 and 18, anddischarge valves 161 and 191 are formed respectively in the valveforming plates 16 and 19. The discharge valves 161 and 191 respectivelyopen and close the discharge ports 151 and 181. Retainers 171 and 201are formed respectively in the retainer forming plates 17 and 20. Theretainer 171 and 201 limit opening degrees of the discharge valves 161and 191.

As shown in FIG. 1, a rotary shaft 21 is rotatably supported to thefront cylinder block 11 and the rear cylinder block 12. A front shafthole 111 and a rear shaft hole 121 extend through the front cylinderblock 11 and the rear cylinder block 12, respectively, and the rotaryshaft 21 is put through the front shaft hole 111 and the rear shaft hole121. An outer peripheral surface of the rotary shaft 21 comes intocontact with an inner peripheral surface of the front shaft hole 111 andthe rear shaft hole 121, and the rotary shaft 21 is directly supportedby the front cylinder block 11 and the rear cylinder block 12 at theinner peripheral surface of the front shaft hole 111 and the rear shafthole 121. An outer peripheral surface portion of the rotary shaft 21which comes into contact with the front shaft hole 111 is a front sealperipheral surface 211, and an outer peripheral surface portion of therotary shaft 21 which comes into contact with the rear shaft hole 121 isa rear seal peripheral surface 212.

A swash plate 23, which serves as a cam body, is firmly attached to therotary shaft 21. The swash plate 23 is accommodated in a swash platechamber 24 defined by the front cylinder block 11 and the rear cylinderblock 12. A lip seal type shaft seal member 22 is arranged between thefront housing member 13 and the rotary shaft 21. The shaft seal member22 prevents a gas leakage through clearance between the front housingmember 13 and the rotary shaft 21. A protruding end portion of therotary shaft 21 protruding to the outside from the front housing member13 is connected to a vehicle engine 26, which is an external drivesource, via an electromagnetic clutch 25. The rotary shaft 21 obtains arotary driving force from the vehicle engine 26 via the electromagneticclutch 25.

As shown in FIG. 2A, a plurality of front cylinder bores 27 are formedin the front cylinder block 11 so as to be arranged around the rotaryshaft 21. As shown in FIG. 2B, a plurality of rear cylinder bores 28 areformed in the rear cylinder block 12 so as to be arranged around therotary shaft 21. Double headed pistons 29 are accommodated respectivelyin the front cylinder bore 27 and the rear cylinder bore 28 forming apair back and force.

As shown in FIG. 1, a rotational motion of the swash plate 23 integrallyrotating with the rotary shaft 21 is transmitted to the double headedpistons 29 via shoes 30, and each double headed piston 29 reciprocatesback and forth within the front cylinder bore 27 and the rear cylinderbore 28. Each double headed piston 29 defines a front compressionchamber 271 within the front cylinder bore 27, and defines a rearcompression chamber 281 within the rear cylinder bore 28.

As shown in FIG. 1, the rotary shaft 21 has in it an in-shaft passage 31extending along a rotation axis 210 of the rotary shaft 21. An inlet 311of the in-shaft passage 31 is positioned in a rear end surface of therotary shaft 21, and is open to the suction chamber 142. The in-shaftpassage 31 has a front outlet 312 and a rear outlet 313. The frontoutlet 312 is open to a front seal peripheral surface 211 of the rotaryshaft 21. The rear outlet 313 is open to a rear seal peripheral surface212.

As shown in FIG. 2A, the front cylinder block 11 has the same number offront communication passages 32 as that of the front cylinder bores 27.Each of the front communication passages 32 connect each of the frontcylinder bores 27 with the front shaft hole 111. As shown in FIG. 2B,the rear cylinder block 12 has the same number of rear communicationpassages 33 as that of the rear cylinder bores 28. Each of the rearcommunication passage 33 communicates each of the rear cylinder bores 28with the rear shaft hole 121. In accordance with the rotation of therotary shaft 21, the front outlet 312 of the in-shaft passage 31intermittently communicates with each of the front communication passage32, and the rear outlet 313 intermittently communicates with each of therear communication passage 33.

In FIG. 1, in the case of a stroke in which the double headed piston 29moves from a left side to a right side, that is, in the case of a statein which the double headed piston 29 sets a certain front cylinder bore27 to a suction stroke, the front outlet 312 communicates thecorresponding front communication passage 32. As a result, a refrigerantwithin the in-shaft passage 31 of the rotary shaft 21 is drawn into thecorresponding front compression chamber 271 via the front outlet 312,and the corresponding front communication passage 32.

In FIG. 1, in the case of a stroke in which the double headed piston 29moves from the right side to the left side, that is, in the case of astate in which the double headed piston 29 sets a certain front cylinderbore 27 to a discharge stroke, the front seal peripheral surface 211shuts off the front outlet 312 from the corresponding frontcommunication passage 32. As a result, the refrigerant within the frontcompression chamber 271 is discharged to the front discharge chamber 131while pushing the discharge valve 161 from the discharge port 151. Therefrigerant discharged to the front discharge chamber 131 flows out toan external refrigerant circuit 34 via a discharge passage 341.

In FIG. 1, in the case of a stroke in which the double headed piston 29moved from the right side to the left side, that is, in the case of astate in which the double headed piston 29 sets a certain rear cylinderbore 28 to a suction stroke, the rear outlet 313 communicates with thecorresponding rear communication passage 33. As a result, therefrigerant within the in-shaft passage 31 of the rotary shaft 21 isdrawn into the corresponding rear compression chamber 281 via the rearoutlet 313 and the corresponding rear communication passage 33.

In FIG. 1, in the case of a stroke in which the double headed piston 29moves from the left side to the right side, that is, in the case of astate in which the double headed piston 29 sets a certain rear cylinderbore 28 to a discharge stroke, the rear seal peripheral surface 212shuts off the rear outlet 313 from the corresponding rear communicationpassage 33. As a result, the refrigerant within the rear compressionchamber 281 is discharged to the rear discharge chamber 141 whilepushing the discharge valve 191 from the discharge port 181. Therefrigerant discharged to the rear discharge chamber 141 flows out tothe external refrigerant circuit 34 via a discharge passage 343.

As shown in FIG. 1, a heat exchanger 37, an expansion valve 38, and aheat exchanger 39 are arranged in the external refrigerant circuit 34.The heat exchanger 37 absorbs heat from the refrigerant. The expansionvalve 38 controls the flow rate of the refrigerant in correspondence toa fluctuation of a gas temperature measured in an outlet of the heatexchanger 39. The heat exchanger 39 transfers the peripheral heat to therefrigerant. The refrigerant flowing out to the external refrigerantcircuit 34 flows back to the suction chamber 142.

As shown in FIG. 1, a portion of the front seal peripheral surface 211of the rotary shaft 21 serves as a first rotary valve 35. A portion ofthe rear seal peripheral surface 212 of the rotary shaft 21 serves as asecond rotary valve 36. In other words, the rotary shaft 21 is a rotaryvalve. Each of the first rotary valve 35 and the second rotary valve 36is integrally formed in the rotary shaft 21. The rotation axis 210 ofthe rotary shaft 21 is a rotation axis of the first rotary valve 35, andalso is a rotation axis of the second rotary valve 36.

As shown in FIG. 1, a rear end surface of the rotary shaft 21, that is,a rear end surface of the second rotary valve 36 intersects the rotationaxis 210 of the rotary valve. The in-shaft passage 31 and the frontoutlet 312 construct an introduction passage of the first rotary valve35. The in-shaft passage 31 and the rear outlet 313 construct anintroduction passage of the second rotary valve 36. The front shaft hole111 is a first valve accommodation chamber accommodating the firstrotary valve 35. The rear shaft hole 121 is a second valve accommodationchamber accommodating the second rotary valve 36.

As shown in FIGS. 3 and 4, the rear housing member 14 has an end wall 40forming the suction chamber 142. A cylinder 41 is integrally formed inan inner surface of the end wall 40. A cylinder interior of the cylinder41 is referred to as a working pressure recess 411, which serves as aworking pressure chamber forming recess. A spool-shaped valve body 42 isslidably fitted into the working pressure recess 411. The valve body 42is provided with a disc-shaped piston portion 43, and a cylinder portion44. The piston portion 43 defines a working pressure chamber 412 withinthe working pressure recess 411. A pressure within the suction chamber142, that is, a suction pressure acts against the pressure within theworking pressure chamber 412 through the valve body 42. A peripheralwall of the cylinder portion 44 has an introduction port 441. In otherwords, the introduction port 441 is open to an outer peripheral surfaceof the cylinder portion 44, and communicates with a cylinder interior442 of the cylinder portion 44. The cylinder interior 442 is an insidepassage of the valve body 42.

As shown in FIGS. 3 and 4, a guide cylinder 45 is integrally formed inan end surface of the rear cylinder block 12 in such a manner as to facethe cylinder 41. A cylinder interior 451 of the guide cylinder 45communicates with an inlet 311 of an in-shaft passage 31, which servesas an introduction passage. A distal end of the guide cylinder 45 isaway from a distal end of the cylinder 41. The cylinder portion 44 ofthe valve body 42 is slidably fitted to the guide cylinder 45. A snapring 46 is attached to an inner peripheral surface of the guide cylinder45, and a first return spring 47 is arranged between the snap ring 46and the piston portion 43. The first return spring 47 urges the valvebody 42 in such a manner that the valve body 42 comes close to the endwall 40 of the rear housing member 14. The closer the valve body 42 tothe end wall 40, the less the volumetric capacity of the workingpressure chamber 412 becomes.

FIG. 3 shows a state in which the valve body 42 is located at acommunication position in such a manner that the valve body 42 allowsthe in-shaft passage 31 to communicate with the suction chamber 142.FIG. 4 shows a state in which the valve body 42 is located at a shutoffposition in such a manner that the valve body 42 shuts off the suctionchamber 142 from the in-shaft passage 31. In other words, in the stateshown in FIG. 3, a whole of the introduction port 441 of the valve body42 is exposed to the interior of the suction chamber 142. The in-shaftpassage 31 communicates with the suction chamber 142 via the cylinderinterior 451 of the guide cylinder 45, the cylinder interior 442 of thecylinder portion 44, and the introduction port 441. In the state shownin FIG. 4, a whole of the introduction port 441 enters the workingpressure recess 411. As a result, the cylinder portion 44 of the valvebody 42 shuts off the in-shaft passage 31 from the suction chamber 142.

As shown in FIGS. 3 and 4, a communication port 401 extends through theend wall 40 of the rear housing member 14. The communication port 401 isopen to the interior of the working pressure chamber 412. A feed port481 of an electromagnetic three-way valve 48 communicates with thecommunication port 401 via a conduit 63. The electromagnetic three-wayvalve 48 serves as a switch valve constructing a working pressureapplying portion.

As shown in FIGS. 3 and 4, the electromagnetic three-way valve 48 has atubular valve housing 49. The valve housing 49 is provided with asmall-diameter cylindrical portion 491 and a large-diameter cylindricalportion 492, and a fixed iron core 50 is accommodated within thesmall-diameter cylindrical portion 491 in a fixed manner. A movable ironcore 51 is slidably fitted into the small-diameter cylindrical portion491. The movable iron core 51 has a flange 511 positioned in thelarge-diameter cylindrical portion 492. An urging spring 52 is arrangedbetween a step 493 between the small-diameter cylindrical portion 491and the large-diameter cylindrical portion 492, and a flange 511. Theurging spring 52 urges the movable iron core 51 in a direction movingthe movable iron core 51 away from the fixed iron core 50. A coil 53 iswound around the small-diameter cylindrical portion 491 in such a manneras to overlap both of the fixed iron core 50 and the movable iron core51. If an electric current is fed to the coil 53, the fixed iron core 50is excited so as to attract the movable iron core 51 against a springforce of the urging spring 52.

As shown in FIGS. 3 and 4, the movable iron core 51 accommodates in it afirst valve body 54. The first valve body 54 faces the fixed iron core50, and selectively contacts and separates from the fixed iron core 50.A valve seat 501 is integrally formed in an end surface of the fixediron core 50 facing the movable iron core 51. An urging spring 55 urgesthe first valve body 54 toward the valve seat 501. The fixed iron core50 has in it a passage 56. The passage 56 extends through the valve seat501. An inlet 561 of the passage 56 communicates with the rear dischargechamber 141 via a conduit 57.

As shown in FIGS. 3 and 4, a lid 58 is fitted to the large-diametercylindrical portion 492 of the valve housing 49. A second valve body 60is fastened to an end surface of the movable iron core 51 facing the lid58. The second valve body 60 selectively contacts and separates from thelid 58. A discharge port 581 extends through the lid 58. The secondvalve body 60 shuts off the discharge port 581 from the cylinderinterior 494 of the large-diameter cylindrical portion 492 in the casethat the second valve body 60 comes into contact with the lid 58. Thedischarge port 581 communicates with the suction chamber 142 via theconduit 59.

As shown in FIGS. 3 and 4, a groove 61 is formed in a peripheral surfaceof the movable iron core 51. The groove 61 communicates with a space 62between the fixed iron core 50 and the movable iron core 51. Thecylinder interior 494 of the large-diameter cylindrical portion 492communicates with the space 62 via the groove 61. The cylinder interior494 of the large-diameter cylindrical portion 492 communicates with theworking pressure chamber 412 via a feed port 481 provided in apenetrating manner in the large-diameter cylindrical portion 492 and aconduit 63.

As shown in FIG. 1, a control computer C controls magnetization anddemagnetization of each of the electromagnetic three-way valve 48 andthe electromagnetic clutch 25. An air conditioner actuating switch 64, aroom temperature setting device 65, and a room temperature detector 66are connected to the control computer C so that signals can betransmitted therebetween. The room temperature setting device 65 sets atarget room temperature, and the room temperature detector 66 detects aroom temperature. In the case that the air conditioner actuating switch64 is in an ON state, the control computer C controls a current feed,that is, a magnetization and demagnetization with respect to theelectromagnetic three-way valve 48 and the electromagnetic clutch 25 onthe basis of a temperature difference between the target roomtemperature and the detected room temperature.

In the case that the detected temperature is lower than the targettemperature, or in the case that the detected temperature is higher thanthe target temperature and the temperature difference between thedetected temperature and the target temperature is equal to or less thanan allowable difference, the control computer C stops feeding theelectric current to the electromagnetic clutch 25. In this case, theelectromagnetic clutch 25 comes to a shut-off state, and a rotationaldriving force of the vehicle engine 26 is not transmitted to the rotaryshaft 21. Further, in the case that the detected temperature is higherthan the target temperature, and the temperature difference between thedetected temperature and the target temperature gets over the allowabledifference, the control computer C feeds the electric current to theelectromagnetic clutch 25. In this case, the electromagnetic clutch 25comes to a coupled state, and the rotational driving force of thevehicle engine 26 is transmitted to the rotary shaft 21.

A timing chart in FIG. 6 shows a clutch waveform K1, a three-way valvewaveform V and a torque waveform T1. The clutch waveform K1 indicates afeed timing of the electric current with respect to the electromagneticclutch 25. The clutch waveform K1 indicates a clutch starting time t1,which is a time for starting a current application to theelectromagnetic clutch 25, and a clutch ending time t2, which is a timefor finishing the current application to the electromagnetic clutch 25.The three-way valve waveform V indicates a feed timing of the electriccurrent to the electromagnetic three-way valve 48. The three-way valvewaveform V has a first exciting period section V1 set in correspondenceto the clutch starting time t1, and a second exciting period section V2set in correspondence to the clutch ending time t2. A starting time t3of the first exciting period section V1 is before the clutch startingtime t1, and an ending time t4 of the first exciting period section V1is after the clutch starting time t1. In other words, the controlcomputer C first carries out the current feed to the electromagneticthree-way valve 48 and thereafter carries out the current feed to theelectromagnetic clutch 25, at a time of starting the current feed to theelectromagnetic clutch 25. A starting time t5 of the second excitingperiod section V2 is before the clutch ending time t2, and the endingtime of the second exciting period section V2 is identical with theclutch ending time t2.

FIG. 5 is a flowchart showing an operation control program forcontrolling an operation of the compressor 10. The control computer Ccontrols the operation of the compressor 10 on the basis of an operationcontrol program shown by the flowchart. A description will be givenbelow of the operation control of the compressor 10 in accordance withthe operation control program shown by the flowchart.

It is assumed that the compressor 10 is in an operation stop state (astate in which the electromagnetic clutch 25 is shut off), and theelectromagnetic three-way valve 48 is in a demagnetized state (a statein which the current application is stopped). In a state in which theelectromagnetic three-way valve 48 is demagnetized, the first valve body54 is away from the valve seat 501 and the second valve body 60 closesthe discharge port 581, as shown in FIG. 3. In the case that theinterior of the working pressure chamber 412 comes to a pressurecorresponding to the discharge pressure, the valve body 42 exists at acommunication position shown in FIG. 3. However, in the case that theinterior of the working pressure chamber 412 comes to a pressurecorresponding to the suction pressure, the valve body 42 exists at ashut-off position shown in FIG. 4.

In step S1, the control computer C determines on the basis of acomparison between the detected temperature and the target temperaturewhether a compressor operation starting mode (a mode for starting thecurrent application to the electromagnetic clutch 25) is established. Inthe case of YES in step S1, that is, in the case that the compressoroperation starting mode is established, the control computer C startsthe current application to the electromagnetic three-way valve 48 instep S2. If the electric current is fed to the electromagnetic three-wayvalve 48, the first valve body 54 comes into contact with the valve seat501 and the passage 56 is closed, as shown in FIG. 4. Further, thesecond valve body 60 is away from the lid 58 and the discharge port 581is opened. In this state, the working pressure chamber 412 communicateswith the suction chamber 142 via the discharge passage constituted bythe communication port 401, the conduit 63, the feed port 481, thecylinder interior 494, the discharge port 581 and the conduit 59.Accordingly, the interior of the working pressure chamber 412 becomesthe same pressure zone as the interior of the suction chamber 142.Therefore, the valve body 42 is securely arranged at the shutoffposition shown in FIG. 4 on the basis of a spring force of the firstreturn spring 47, and the communication between the introduction port441 and the suction chamber 142 is shut off.

In step S3, the control computer C determines whether a period ta[(t1−t3)=ta in the case illustrated in FIG. 6] has elapsed from thestart of the current application to the electromagnetic three-way valve48. In the case of YES in step S3, that is, in the case that the periodta has elapsed from the start of the current application to theelectromagnetic three-way valve 48, the control computer C starts thecurrent application to the electromagnetic clutch 25 in step S4.Accordingly, the electromagnetic clutch 25 gives way to the coupledstate from the shutoff state, and the rotary shaft 21 and the swashplate 23 start rotating.

In step S5, the control computer C determines whether a period tb[(t4−t1)=tb in the case illustrated in FIG. 6] has elapsed from thestart of the current application to the electromagnetic clutch 25. Inthe case of YES in step S5, that is, in the case that the period tb haselapsed from the start of the current application to the electromagneticclutch 25, the control computer C stops the current application to theelectromagnetic three-way valve 48 in step S6. If the current feed tothe electromagnetic three-way valve 48 is stopped, the first valve body54 is away from the valve seat 501 and the passage 56 is opened, asshown in FIG. 3. Further, the second valve body 60 comes into contactwith the lid 58 and the discharge port 581 is closed. In this state, thecommunication between the suction chamber 142 and the working pressurechamber 412 is shut off. The working pressure chamber 412 communicateswith the rear discharge chamber 141 via the feed passage constituted bythe communication port 401, the conduit 63, the feed port 481, thecylinder interior 494, the groove 61, the space 62, the passage 56 andthe conduit 57. Accordingly, the refrigerant pressure (the dischargepressure) within the rear discharge chamber 141 is introduced to theworking pressure chamber 412, and the interior of the working pressurechamber 412 becomes same pressure zone as the interior of the reardischarge chamber 141. The communication port 401 and the conduit 63which is a common passage connecting the working pressure chamber 412 tothe electromagnetic three-way valve 48.

The pressure (the working pressure) of the refrigerant within the reardischarge chamber 141 is higher than the pressure within the cylinderinterior 442, and the pressure within the working pressure chamber 412arranges the valve body 42 at the communication position shown in FIG. 3against the pressure of the cylinder interior 442 and the spring forceof the first return spring 47. Accordingly, the introduction port 441 isexposed into the suction chamber 142, and the introduction port 441communicates with the suction chamber 142. Therefore, the refrigerantwithin the suction chamber 142 flows into the in-shaft passage 31 viathe introduction port 441.

After stopping the current application to the electromagnetic three-wayvalve 48, the computer C determines on the basis of the comparisonbetween the detected temperature and the target temperature whether acompressor operation stopping mode (a mode for stopping the currentapplication to the electromagnetic clutch 25) is established, in stepS7. In the case of YES in step S7, that is, in the case that thecompressor operation stopping mode is established, the control computerC starts the current application to the electromagnetic three-way valve48 in step S8. If the current application to the electromagneticthree-way valve 48 is started, the communication between the workingpressure chamber 412 and the rear discharge chamber 141 is shut off, andthe working pressure chamber 412 communicates with the suction chamber142. In other words, the working pressure corresponding to the dischargepressure within the working pressure chamber 412 is discharged to thesuction chamber 142. In other words, the working pressure within theworking pressure chamber 412 is released.

In step S9, the control computer C determines whether a period tc[(t2−t5)=tc in the case illustrated in FIG. 6] has elapsed from thestart of the current application to the electromagnetic three-way valve48. In the case of YES in step S9, that is, in the case that the periodtc has elapsed from the start of the current application to theelectromagnetic three-way valve 48, the control computer C stops thecurrent application to the electromagnetic three-way valve 48 and theelectromagnetic clutch 25 in step S10. After the process of step S10,the control computer C gives way to step S1.

The torque waveform T1 in FIG. 6 is one example of the torquefluctuation. In the case that the current application to theelectromagnetic clutch 25 is started, the torque is fluctuated. Thepresent embodiment excites the electromagnetic three-way valve 48 beforestarting the current application to the electromagnetic clutch 25, andstops the current application to the electromagnetic three-way valve 48after starting exciting the electromagnetic clutch 25, at a time ofstarting the current application to the electromagnetic clutch 25. As aresult, a rapid torque fluctuation [a fluctuation portion T11 in thetorque waveform T1] at a time when the current application to theelectromagnetic clutch 25 is started is suppressed. Further, even whenthe current application to the electromagnetic clutch 25 is stopped, thetorque is fluctuated. The present embodiment excites the electromagneticthree-way valve 48 before stopping the current application to theelectromagnetic clutch 25, at a time of stopping the current applicationto the electromagnetic clutch 25. As a result, the rapid torquefluctuation at a time when the current application to theelectromagnetic clutch 25 is stopped is suppressed.

The electromagnetic three-way valve 48, the working pressure chamber 412and the valve body 42 construct a switch portion. The switch portion iscapable of switching the suction chamber 142, which is a portion of thesuction pressure zone within the compressor 10, to a state in which thesuction chamber 142 communicates with the front outlet 312 and the rearoutlet 313 of the in-shaft passage 31, which is an introduction passage,and a state in which the suction chamber 142 is shut off from the frontoutlet 312 and the rear outlet 313. In FIGS. 1 and 3, theelectromagnetic three-way valve 48 is in a first state (a demagnetizedstate) in which the three-way valve 48 can feed the refrigerant in therear discharge chamber 141, which is a discharge pressure zone, to theworking pressure chamber 412. In FIG. 4, the electromagnetic three-wayvalve 48 is in a second state (a magnetized state) in which thethree-way valve 48 can feed the refrigerant in the rear dischargechamber 141, which is a discharge pressure zone to the working pressurechamber 412.

The first embodiment has the following advantages.

(1) In the state in which the pressure within the rear discharge chamber141, which is the working pressure, is not introduced to the workingpressure chamber 412, the valve body 42 is arranged at the shutoffposition shown in FIG. 4. If the valve body 42 is arranged at theshutoff position, the suction chamber 142, which is a suction pressurezone within the compressor 10, is shut off from the introduction port441. Since the rotation of the rotary shaft 21 is started after thevalve body 42 is previously arranged at the shutoff position, at a timewhen the operation of the compressor 10 is started (at a time when therotation of the rotary shaft 21 is started), the refrigerant does notflow in the cylinder interior 442 and the in-shaft passage 31 from thesuction chamber 142. Accordingly, the rapid torque fluctuation issuppressed, and a starting impact is reduced. Further, since thecommunication between the suction chamber 142 within the compressor 10and the introduction port 441 is shut off, the amount of the refrigerantcompressed in the front compression chamber 271 and the rear compressionchamber 281 at a time when the valve body 42 exists at the shutoffposition is small. Therefore, the effect of suppressing the torquefluctuation, that is, the effect of reducing the starting impact isimproved.

(2) If the working pressure within the working pressure chamber 412 isreleased, the valve body 42 is returned to the shutoff position by thespring force of the first return spring 47. The use of the first returnspring 47 simplifies the structure for returning the valve body 42 tothe shutoff position.

(3) In the case that the valve body 42 exists at the shutoff position,the introduction port 441, which is an inlet of the cylinder interior442 of the valve body 42, enters the working pressure recess 411 so asto be shielded, and in the case that the valve body 42 exists at thecommunication position, the introduction port 441 is out of the workingpressure recess 411 so as to be exposed to the interior of the suctionchamber 142. The structure in which the introduction port 441 comes inand out with respect to the interior of the working pressure recess 411enlarges the introduction port 441, and is preferable for securing asufficient passage cross-sectional area of the introduction passage.

FIG. 7 explains a second embodiment in accordance with the presentinvention. The structure of the apparatus is the same as the case of thefirst embodiment.

In the second embodiment, the structure of the apparatus is the same asthe case of the first embodiment, however, the second embodiment isdifferent from the first embodiment in a point that the amount of thecurrent application is gradually increased at a time of starting thecurrent application to the electromagnetic clutch 25, as shown by acurrent application starting section K21 in a clutch waveform K2. Thecurrent application to the electromagnetic three-way valve 48 is stoppedafter the feed current value becomes maximum. The fluctuation of thefluctuation portion T21 in the torque waveform T2 expressing the torquefluctuation is suppressed more than the case of the first embodiment, onthe basis of the current application start mentioned above to theelectromagnetic clutch 25.

For example, in the conventional fixed displacement type pistoncompressor having no switch portion, the torque at a time of starting isgreat, that is, the load applied to the electromagnetic clutch 25 isgreat. Accordingly, if the amount of the current application isgradually increased in the same manner as the present invention, in theconventional compressor, a slip is generated in the electromagneticclutch 25. Therefore, in the conventional compressor, it is hard tosecure a reliability of the electromagnetic clutch 25.

In the present embodiment, since the torque at a time of starting issmall, that is, the load applied to the electromagnetic clutch 25 issmall, it is possible to carry out an operation control such as togradually increase the amount of the current application to theelectromagnetic clutch 25.

FIGS. 8 and 9 explain a third embodiment. The same reference numeralsare attached to the same components as those of the first embodiment.

As shown in FIG. 8, a check valve 68 is arranged in a portion 34A of anexternal refrigerant circuit 34 in an upstream side of the heatexchanger 37, and the portion 34A of the external refrigerant circuit 34in the upstream side of the check valve 68 is connected to the workingpressure chamber 412 by the communication port 401 and the inflowpassage L. The check valve 68 is provided in the portion 34A of theexternal refrigerant circuit 34 in a downstream side of a connectionportion between the portion 34A of the external refrigerant circuit 34and the inflow passage L. The interior of the portion 34A of theexternal refrigerant circuit 34 is a discharge pressure zone. Anelectromagnetic on-off valve 67 is arranged in the inflow passage L. Theelectromagnetic on-off valve 67 and the check valve 68 construct aworking pressure applying portion. The electromagnetic on-off valve 67,which serves as a switch valve, is under the magnetizing anddemagnetizing control of the control computer C. In FIG. 8, theelectromagnetic on-off valve 67 is in a magnetized state, and theelectromagnetic on-off valve 67 is in an open state, in which the inflowpassage L is opened. In the case that the electromagnetic on-off valve67 is in the magnetized state, the refrigerant (the dischargerefrigerant) in the portion 34A of the external refrigerant circuit 34in the upstream side of the check valve 68 can flow in the workingpressure chamber 412. In FIG. 9A, the electromagnetic on-off valve 67 isin the demagnetized state, and the electromagnetic on-off valve 67 is ina closed state, in which the inflow passage L is shut off. Theelectromagnetic on-off valve 67 is a normally closed typeelectromagnetic on-off valve which is closed in a non-excited state (ademagnetized state). However, even in the case that the electromagneticon-off valve 67 is in the closed state, some amount of gas can leak.

A waveform W1 in a timing chart in FIG. 9B shows a feed timing of theelectric current with respect to the electromagnetic on-off valve 67.The current application to the electromagnetic on-off valve 67 isstarted after [for example, after one second, (t6−t1) after in theillustrated example] the current application to the electromagneticclutch 25 is started, and the current application stop after the currentapplication to the electromagnetic on-off valve 67 is the same as theending time with respect to the electromagnetic clutch 25 [the currentapplication is stopped at a clutch ending time t2 in the example in FIG.9B].

In the case that the current application to the electromagnetic clutch25 is stopped, the current application to the electromagnetic on-offvalve 67 is simultaneously stopped, and the electromagnetic on-off valve67 gives way to the closed state from the open state. If the currentapplication to the electromagnetic clutch 25 is stopped, that is, if theoperation of the compressor 10 is stopped, the refrigerant is notdischarged, so that the check valve 68 is closed. Accordingly, thebalancing of the pressure within the compressor 10 is rapidly advanced.

In the case that the operation of the compressor 10 is stopped, theelectromagnetic on-off valve 67 is in the closed state. However, sincesome amount of gas can leak in the electromagnetic on-off valve 67, therefrigerant having the discharge pressure remaining within the workingpressure chamber 412 and within a portion of the inflow passage Lbetween the communication port 401 and the electromagnetic on-off valve67 leaks out to the portion 34A in the external refrigerant circuit 34in the upstream side of the check valve 68 via the electromagneticon-off valve 67. Accordingly, the balancing of the pressure within theworking pressure chamber 412 is advanced. Therefore, the valve body 42is arranged at the shutoff position shown in FIG. 9A on the basis of thespring force of the first return spring 47 by a time point [a time t1 inthe example in FIG. 9B] when the current application to theelectromagnetic clutch 25 is next started.

The electromagnetic on-off valve 67 is in the demagnetized state (theclosed state) before the current application to the electromagneticclutch 25 is started, and the current application to the electromagneticon-off valve 67 is started after the current application to theelectromagnetic clutch 25. Accordingly, the valve body 42 is in a stateof being at the shutoff position for some amount of time after thecurrent application to the electromagnetic clutch 25 is started, and therefrigerant within the suction chamber 142 does not flow in the in-shaftpassage 31. Therefore, the starting impact at a time of starting thecompressor 10 is reduced.

If the current application to the electromagnetic on-off valve 67 isstarted after the current application to the electromagnetic clutch 25is started, the electromagnetic on-off valve 67 gives way to the openstate from the closed state, and the portion 34A of the externalrefrigerant circuit 34 in the upstream side of the check valve 68communicates with the working pressure chamber 412. After starting thecurrent application to the electromagnetic clutch 25 (that is, after theoperation of the compressor 10 is started), the check valve 68 ismaintained in the open state on the basis of the discharge of therefrigerant, and the discharged refrigerant is circulated to the suctionchamber 142 via the external refrigerant circuit 34. In the case inwhich the current application to the electromagnetic clutch 25 ismaintained (that is, a state in which the compressor 10 is operated),the electromagnetic on-off valve 67 is maintained in the open state, andthe refrigerant pressure (the discharge pressure) in the portion 34A ofthe external refrigerant circuit 34 in the upstream side of the checkvalve 68 is applied to the working pressure chamber 412 via the inflowpassage L and the electromagnetic on-off valve 67. Accordingly, thevalve body 42 is arranged at a communication position shown in FIG. 8.

The check valve 68, the electromagnetic on-off valve 67, the workingpressure chamber 412, and the valve body 42 construct a switch portion.The switch portion is capable of switching the suction chamber 142,which is a portion of the suction pressure zone within the compressor10, to a communication state, in which the suction chamber 142communicates with the front outlet 312 and the rear outlet 313 in theintroduction passage, and a shutoff state, in which the suction chamber142 is shut off from the front outlet 312 and the rear outlet 313. InFIG. 8, the electromagnetic on-off valve 67 is in a first state (amagnetized state), in which the on-off valve 67 can feed the refrigerantin the portion 34A of the external refrigerant circuit 34, which is adischarge pressure zone, to the working pressure chamber 412. In FIG.9A, the electromagnetic on-off valve 67 is in a second state (ademagnetized state), in which the on-off valve cannot feed therefrigerant in the portion of the external refrigerant circuit 34 to theworking pressure chamber 412.

The third embodiment has the same advantages as those of the firstembodiment.

FIGS. 10 to 11B explain a fourth embodiment. The same reference numeralsare attached to the same components as those of the third embodiment.

In the fourth embodiment, a normally open type electromagnetic on-offvalve 67A is used in place of the normally closed type electromagneticon-off valve 67 in the third embodiment. The normally open typeelectromagnetic on-off valve 67A is opened in the non-excited state, andis closed in the excited state. In FIG. 10, the electromagnetic on-offvalve 67A, which serves as a switch valve, opens the inflow passage L inthe non-excited state. In FIG. 11A, the electromagnetic on-off valve 67Acloses the inflow passage L in the excited state. The electromagneticon-off valve 67A and the check valve 68 construct the working pressureapplying portion.

A waveform W2 in a timing chart in FIG. 11B shows a current feed timingwith respect to the electromagnetic on-off valve 67A. At a time when thecurrent application to the electromagnetic clutch 25 is started, thecurrent application to the electromagnetic on-off valve 67A has alreadybeen started [at a time t3 in the illustrated example] before thecurrent application to the electromagnetic clutch 25 is started [at atime t1 in the illustrated example], and the current application to theelectromagnetic on-off valve 67A is stopped [at a time t4 in theillustrated example] after the current application to theelectromagnetic clutch 25 is started.

If the operation of the compressor 10 is stopped, the refrigerant is notdischarged, so that the check valve 68 is closed. Accordingly, thebalancing of the pressure within the compressor 10 is rapidly advanced.In the case that the operation of the compressor 10 is stopped, theelectromagnetic on-off valve 67A is in the open state. Accordingly, therefrigerant having the discharge pressure remaining within the workingpressure chamber 412, and within a portion of the inflow passage Lbetween the communication port 401 and the electromagnetic on-off valve67A leaks out to the portion 34A of the external refrigerant circuit 34in the upstream side of the check valve 68 via the electromagneticon-off valve 67A. Therefore, the balancing of the pressure within theworking pressure chamber 412 is rapidly advanced. Accordingly, the valvebody 42 is arranged at a shutoff position shown by FIG. 11A on the basisof the spring force of the first return spring 47 by a time point whenthe current application to the electromagnetic clutch 25 is nextstarted. The valve body 42 is located at the shutoff position over atime period from before the current application to the electromagneticclutch 25 is started [(t1−t3) before in the illustrated example] toafter the current application is started [(t4−t1) after in theillustrated example], and the refrigerant within the suction chamber 142does not flow in the in-shaft passage 31. Accordingly, the startingimpact at a time of starting the compressor 10 is reduced.

The check valve 68, the electromagnetic on-off valve 67A, the workingpressure chamber 412 and the valve body 42 construct a switch portion.The switch portion is capable of switching the suction chamber 142,which is a portion of the suction pressure zone within the compressor10, to a state in which the suction chamber 142 communicates with theoutlet of the introduction passage, and a state in which the suctionchamber 142 is shut off. In FIG. 10, the electromagnetic on-off valve67A is in a first state (a demagnetized state), in which the refrigerantin the portion 34A of the external refrigerant circuit 34, which is adischarge pressure zone, can be fed to the working pressure chamber 412.In FIG. 11A, the electromagnetic on-off valve 67 is in a second state (amagnetized state), in which the refrigerant in the portion 34A of theexternal refrigerant circuit 34 cannot be fed to the working pressurechamber 412.

The fourth embodiment has the same advantages as those of the firstembodiment.

FIGS. 12A and 12B explain a fifth embodiment in accordance with thepresent invention. The same reference numerals are used in the samecomponents as those of the first embodiment.

A guide cylinder 45A fitted to the cylinder portion 44 of the valve body42 is formed as a closed-end cylindrical shape, and is formedindependently from the rear cylinder block 12, the rotary shaft 21 andthe like. A bottom wall of the guide cylinder 45A comes into contactwith an end surface 122 of the rear cylinder block 12. The guidecylinder 45A is fitted to the cylinder portion 44 of the valve body 42in such a manner as to be allowed to move in a radial direction of therotary shaft 21 with respect to the rotary shaft 21. A communicationport 452 is formed in a bottom wall of the guide cylinder 45A in such amanner as to connect the cylinder interior 451 of the guide cylinder 45Awith the in-shaft passage 31. The first return spring 47 is arrangedbetween the bottom wall of the guide cylinder 45A and the piston portion43. The valve body 42 is arranged at a communication position in FIG.12A, and the valve body 42 is arranged at a shutoff position in FIG.12B. The magnetizing and demagnetizing timings of the electromagneticthree-way valve 48 are identical with the case of the first embodiment.

On the assumption that the refrigerant leaks through clearance betweenthe valve body 42 and the cylinder 41 or clearance between the valvebody 42 and the guide cylinder at a time when the valve body 42 is in astate of being at the shutoff position, the effect of reducing thestarting impact is lowered.

However, the guide cylinder 45A of the present embodiment is fitted tothe cylinder portion 44 of the valve body 42 in such a manner that theguide cylinder 45A is allowed to move in the radial direction of therotary shaft 21 with respect to the rotary shaft 21. Accordingly, anaxis 413 of the working pressure recess 411 is allowed to come into linewith an axis 453 of the guide cylinder 45A. Therefore, it is possible toreduce a clearance between the cylinder portion 44 of the valve body 42and the cylinder 41 and a clearance between the cylinder portion 44 ofthe valve body 42 and the guide cylinder 45A, and it is possible toprevent the refrigerant from leaking along a peripheral surface of thecylinder portion 44 of the valve body 42.

FIGS. 13 and 14 explain a sixth embodiment. The same reference numeralsare used in the same components as those of the first embodiment.

A piston 69 is slidably fitted to the cylinder 41, and a transmissionrod 70 is coupled to the piston 69. The piston 69 defines the workingpressure chamber 412 within the working pressure recess 411. Thetransmission rod 70 enters an in-shaft passage 31A. The in-shaft passage31A is provided with a small-diameter passage 314, and a large-diameterpassage 315 having a larger diameter than the small-diameter passage314. A cylindrical small circumferential surface body 71 is fastened toa portion of the transmission rod 70 positioned within thesmall-diameter passage 314. A cylindrical large circumferential surfacebody 72 is fastened to a portion of the transmission rod 70 positionedwithin the large-diameter passage 315. The cylindrical smallcircumferential surface body 71 is fitted to the small-diameter passage314 in such a manner as to be slidable in a direction of a rotation axis210 of the rotary shaft 21, and be capable of opening and closing thefront outlet 312, and the cylindrical large circumferential surface body72 is fitted to the large-diameter passage 315 in such a manner as to beslidable in the direction of the rotation axis 210 of the rotary shaft21, and be capable of opening and closing the rear outlet 313. Theinterior of the cylindrical large circumferential surface body 72communicates a portion of the in-shaft passage 31A between the smallcircumferential surface body 71 and the large circumferential surfacebody 72 with a portion of the in-shaft passage 31A between the inlet 311of the in-shaft passage 31A and the large circumferential surface body72.

A first return spring 73 is arranged between a step 316 between thesmall-diameter passage 314 and the large-diameter passage 315, and thelarge circumferential surface body 72. The first return spring 73 urgesa whole of the small circumferential surface body 71, the largecircumferential surface body 72, the transmission rod 70 and the piston69 toward the working pressure chamber 412 in such a manner as to pressthe piston 69 to the working pressure recess 411. The smallcircumferential surface body 71, the large circumferential surface body72, the transmission rod 70 and the piston 69 construct a valve bodydefining the working pressure chamber 412 within the working pressurerecess 411.

FIG. 14 shows a state in which the small circumferential surface body 71closes the front outlet 312, and the large circumferential surface body72 closes the rear outlet 313. The front outlet 312 and the rear outlet313 are shut off from the in-shaft passage 31A. FIG. 13 shows a state inwhich the small circumferential surface body 71 opens the front outlet312, and the large circumferential surface body 72 opens the rear outlet313. The front outlet 312 and the rear outlet 313 communicate with thein-shaft passage 31A. If the current application to the electromagneticthree-way valve 48 is carried out, the small circumferential surfacebody 71 and the large circumferential surface body 72 are arranged at ashutoff position shown in FIG. 14 from a communication position shown inFIG. 13, on the basis of a spring force of the first return spring 73.The magnetizing and demagnetizing timings of the electromagneticthree-way valve 48 are identical with the case of the first embodiment.

The sixth embodiment has the same advantages as those of the firstembodiment. Further, in the sixth embodiment, since the refrigerantwhich can flow in the front compression chamber 271 and the rearcompression chamber 281 at a time when the small circumferential surfacebody 71 and the large circumferential surface body 72 are at the shutoffposition is constituted only by the refrigerant within the front outlet312, within the rear outlet 313, within the front communication passage32, and within the rear communication passage 33, the effect of reducingthe starting impact is more noticeable than the case of the firstembodiment.

In the case that the piston 69 is structured such as to be relativelyrotatable with respect to the transmission rod 70, the piston 69prevents the relative rotation between the first return spring 73 andthe rotary shaft 21. Accordingly, it is possible to avoid an abrasionand damage of the first return spring 73 or the rotary shaft 21 causedby the relative rotation between the first return spring 73 and therotary shaft 21. Alternatively, the large circumferential surface body72 may be structured such as to be relatively rotatable with respect tothe first return spring 73.

FIGS. 15A and 15B explain a seventh embodiment. The same referencenumerals are used in the same components as those of the sixthembodiment.

A disc-shaped circular plate 74 is fastened to a distal end of thetransmission rod 70. As shown in FIG. 15A, in the case that the largecircumferential surface body 72 is located at a position at which thelarge circumferential surface body 72 closes the rear outlet 313, thecircular plate 74 is located in an upstream side of the front outlet 312within the in-shaft passage 31A, and the refrigerant in the in-shaftpassage 31A cannot flow in the front compression chamber 271 via thefront outlet 312. As shown in FIG. 15B, in the case that the largecircumferential surface body 72 is located at a position at which thelarge circumferential surface body 72 opens the rear outlet 313, thecircular plate 74 is located in a downstream side of the front outlet312 within the in-shaft passage 31A, and the refrigerant in the in-shaftpassage 31A can flow in the front compression chamber 271 via the frontoutlet 312. If the electromagnetic three-way valve 48 [refer to FIG. 14]is excited, the circular plate 74 is arranged at a shutoff positionshown in FIG. 15A from a communication position shown in FIG. 15B, onthe basis of the spring force of the first return spring 73. Thecircular plate 74, the large circumferential surface body 72, thetransmission rod 70 and the piston 69 construct the valve body definingthe working pressure chamber 412 within the working pressure recess 411.

The seventh embodiment has the same advantages as those of the sixthembodiment.

FIGS. 16A and 16B explain an eighth embodiment. The same referencenumerals are used in the same components as those of the sixthembodiment.

A cylinder 75 is coupled to the piston 69 so as to be relativelyrotatable with respect to the piston 69. The cylinder 75 is slidablyfitted to the in-shaft passage 31A. An end wall 752 is formed in adistal end of the cylinder 75. An angular pin 76 is fastened to an innerend which is a dead end of the in-shaft passage 31A, and the angular pin76 is inserted to the end wall 752 of the cylinder 75 so as to berelatively slidable. The cylinder 75 and the angular pin 76 areintegrally rotated with the rotary shaft 21, and can slide within thein-shaft passage 31A in a state in which the angular pin 76 is insertedto the end wall 752.

The cylinder 75 is provided with a small-diameter cylindrical portion77, which is fitted into the small-diameter passage 314, and alarge-diameter cylindrical portion 78, which is fitted to thelarge-diameter passage 315. An introduction port 751 is formed in aportion of the large-diameter cylindrical portion 78 positioned withinthe suction chamber 142 so as to be capable of connecting the suctionchamber 142 with a cylinder interior 750 of the cylinder 75.

A communication port 771 is formed in a portion of the small-diametercylindrical portion 77 within the small-diameter passage 314 so as tocommunicate with the inside of the small-diameter cylindrical portion77. A communication port 781 is formed in the large-diameter cylindricalportion 78 so as to communicate with the interior of the large-diametercylindrical portion 78.

The first return spring 73 is arranged between a step 753 between thesmall-diameter cylindrical portion 77 and the large-diameter cylindricalportion 78, and the step 316 of the rotary shaft 21. The first returnspring 73 urges the cylinder 75 toward the working pressure chamber 412in such a manner as to press the piston 69 to the working pressurerecess 411. The piston 69 and the cylinder 75 construct a valve bodydefining the working pressure chamber 412 within the working pressurerecess 411.

FIG. 16B shows a state in which the small-diameter cylindrical portion77, which serves as a valve body, closes the front outlet 312, and showsa state in which the large-diameter cylindrical portion 78, which servesas a valve body, closes the rear outlet 313. Accordingly, the frontoutlet 312 and the rear outlet 313 are shut off from the cylinderinterior 750 of the cylinder 75. FIG. 16A shows a state in which thecommunication port 771 of the small-diameter cylindrical portion 77communicates with the front outlet 312, and shows a state in which thecommunication port 781 of the large-diameter cylindrical portion 78communicates with the rear outlet 313, and the front outlet 312 and therear outlet 313 communicate with the cylinder interior 750. Therefrigerant in the suction chamber 142 can flow in the front compressionchamber 271 via the introduction port 751, the cylinder interior 750,the communication port 771, the front outlet 312, and the frontcommunication passage 32, and the refrigerant in the suction chamber 142can flow in the rear compression chamber 281 via the introduction port751, the cylinder interior 750, the communication port 781, the rearoutlet 313, and the rear communication passage 33. If theelectromagnetic three-way valve 48 [refer to FIG. 14] is excited, thecylinder 75 is arranged from a communication position shown in FIG. 16Ato a shutoff position shown in FIG. 16B on the basis of the spring forceof the first return spring 73. The magnetizing and demagnetizing timingsof the electromagnetic three-way valve 48 are the same as those of thefirst embodiment.

The eighth embodiment has the same advantages as those of the sixthembodiment.

FIGS. 17 to 18B explain a ninth embodiment. The same reference numeralsare used in the same components as those of the fifth embodiment.

As shown in FIG. 17, a check valve built-in type oil separator 79 isarranged in the portion 34A of the external refrigerant circuit 34 whichis located in an upstream side of the heat exchanger 37.

As shown in FIGS. 18A and 18B, a refrigerant swirling cylinder 81 isfixed in a fitting manner into a housing 80 constructing the oilseparator 79. The refrigerant swirling cylinder 81 defines an oilseparation chamber 82 and a valve accommodation chamber 83 in thehousing 80. The oil separation chamber 82 communicates with the portion34A of the external refrigerant circuit 34 which is located in theupstream side of the oil separator 79, and the refrigerant in theportion 34A of the external refrigerant circuit 34 flows into the oilseparation chamber 82. The refrigerant flowing into the oil separationchamber 82 from the portion 34A of the external refrigerant circuit 34swirls around the refrigerant swirling cylinder 81. The refrigerantswirling around the refrigerant swirling cylinder 81 flows in a cylinderinterior 812 from a cylinder port 811 of the refrigerant swirlingcylinder 81 facing the oil separation chamber 82.

A valve body 85 is accommodated in the valve accommodation chamber 83.The valve body 85 is capable of opening and closing the other cylinderport 813 of the refrigerant swirling cylinder 81. The valve body 85 isurged toward a position closing the cylinder port 813 by a compressionspring 86. If a pressure of the refrigerant within the cylinder interior812 overcomes a spring force of the compression spring 86, therefrigerant of the cylinder interior 812 pushes the valve body 85 so asto flow out to the valve accommodation chamber 83. The refrigerantswirling cylinder 81, the valve body 85 and the compression spring 86construct a check valve 87. The refrigerant in the valve accommodationchamber 83 flows in the heat exchanger 37.

A constriction hole 402 extends through the end wall 40. Theconstriction hole 402, which serves as a constriction, connects theworking pressure chamber 412 with a conduit 84. The oil separationchamber 82 communicates with the working pressure chamber 412 via theconduit 84 and the constriction hole 402. The pressure (the dischargepressure) within the oil separation chamber 82 is applied to the workingpressure chamber 412 via the conduit 84 and the constriction hole 402.The constriction hole 402 and the conduit 84 construct a portion of aninflow passage which is located in a downstream side of the oilseparator 79.

The oil is charged within the circuit constituted by the compressor 10and the external refrigerant circuit 34, and the oil flows with therefrigerant.

The refrigerant flowing in the oil separation chamber 82 from theportion 34A of the external refrigerant circuit 34 swirls around therefrigerant swirling cylinder 81, and a mist-like oil flowing togetherwith the refrigerant is separated within the oil separation chamber 82.The refrigerant swirling around the refrigerant swirling cylinder 81flows in the cylinder interior 812, and the oil separated from therefrigerant can flow in the working pressure chamber 412 via the conduit84 and the constriction hole 402. The conduit 84 and the constrictionhole 402 construct an inflow passage reaching the portion 34A of theexternal refrigerant circuit 34, which is a discharge pressure zone,from the working pressure chamber 412.

In the case that the operation of the compressor 10 stops and thepressure within the compressor 10 is balanced, the valve body 42 isretained at a shutoff position shown in FIG. 18B on the basis of thespring force of the first return spring 47. In the case that theoperation of the compressor 10 is started, the refrigerant does not flowin the in-shaft passage 31 from the suction chamber 142, so that thestarting impact is reduced.

If the pressure within the oil separation chamber 82 is increased inaccordance with the start of the operation of the compressor 10, thepressure within the working pressure chamber 412 is also increased, andthe valve body 42 is arranged at the communication position shown inFIG. 18A against the spring force of the first return spring 47. Sincethe constriction hole 402 narrows a passage cross-sectional area betweenthe conduit 84 and the working pressure chamber 412, the pressure withinthe working pressure chamber 412 is not rapidly increased even if thepressure within the front discharge chamber 131 and the rear dischargechamber 141 is increased. Further, since the oil separated by the oilseparator 79 enters the constriction hole 402, the oil entering theconstriction hole 402 generates a passage resistance so as to contributeto a suppression of a rapid increase of the pressure within the workingpressure chamber 412. Since the rapid increase of the pressure withinthe working pressure chamber 412 is suppressed, the valve body 42 is notmoved from the shutoff position to the communication position in amoment of time. Accordingly, the reducing effect of the starting impactis increased.

Since the ninth embodiment does not use the electromagnetic three-wayvalve 48 and the electromagnetic on-off valve 67, the ninth embodimentis advantageous in cost compared with those of the first to the fifthembodiments.

FIGS. 19A and 19B explain a tenth embodiment. The same referencenumerals are used in the same components as those of the firstembodiment.

A communication chamber 88 and a valve hole 891 are formed in the rearhousing member 14, and a plate-shaped opening and closing plate 90 isaccommodated within the communication chamber 88 in such a manner as tobe capable of opening and closing the valve hole 891. The valve hole 891extends through a partition wall 89 which separates the communicationchamber 88 and the suction chamber 142. An inlet 311 of the in-shaftpassage 31 is positioned at an end surface of the rotary shaft 21 withinthe rear cylinder block 12, and is open to the communication chamber 88within the rear housing member 14.

A piston 91 is fitted into the working pressure recess 411, and atransmission rod 92 is integrally formed in the piston 91. The openingand closing plate 90 is fastened to a distal end of the transmission rod92. A flat valve seat surface 892 is formed in a surface of thepartition wall 89 facing the communication chamber 88. The opening andclosing plate 90 selectively contacts and separates from the valve seatsurface 892. A seal surface 901 of the opening and closing plate 90coming into contact with the valve seat surface 892 is formed as a flatsurface. In other words, in the case that the opening and closing plate90 closes the valve hole 891, the seal surface 901 of the opening andclosing plate 90 comes into surface contact with the valve seat surface892. The piston 91, the transmission rod 92 and the opening and closingplate 90 define the working pressure chamber 412 within the workingpressure recess 411, and construct a valve body 93 opening and closingthe valve hole 891.

A first return spring 94 is arranged between the piston 91 and thepartition wall 89. The first return spring 94 urges the piston 91 in adirection in which the first return spring 94 presses the piston 91 tothe working pressure recess 411. The valve body 93 in FIG. 19B islocated at a communication position at which the valve body 93 connectsthe communication chamber 88 with the suction chamber 142 by opening thevalve hole 891, and the valve body in FIG. 19A is located at a shutoffposition at which the valve body 93 shuts off the communication chamber88 from the suction chamber 142 by closing the valve hole 891. The firstreturn spring 94 urges the valve body 93 from the communication positiontoward the shutoff position.

A plurality of stoppers 902 are provided in a protruding manner in aback surface of the opening and closing plate 90 facing the end surfaceof the rotary shaft 21. The stopper 902 selectively contacts andseparates from a distal end of a cylindrical portion 123 provided in aprotruding manner in an end surface 122 of the rear cylinder block 12.In a state in which the valve body 93 is arranged at the communicationposition shown in FIG. 19B, the stopper 902 is brought into contact withthe distal end of the cylindrical portion 123, and in a state in whichthe valve body 93 is arranged at the shutoff position shown in FIG. 19A,the stopper 902 is away from the distal end of the cylindrical portion123.

In a state in which the electromagnetic three-way valve 48 ismagnetized, the valve body 93 is arranged at the shutoff position shownin FIG. 19A, and the refrigerant within the suction chamber 142 cannotflow in the communication chamber 88. In a state in which theelectromagnetic three-way valve 48 is demagnetized, the valve body 93 isarranged at the communication position shown in FIG. 19B, and therefrigerant within the suction chamber 142 can flow in the frontcompression chamber 271 (refer to FIG. 1) and the rear compressionchamber 281 via the communication chamber 88 and the in-shaft passage31.

The magnetizing and demagnetizing timings of the electromagneticthree-way valve 48 are the same as the case of the first embodiment.Accordingly, the tenth embodiment also obtains the reducing effect ofthe starting impact. Further, since it is possible to reduce thevolumetric capacity of the communication chamber 88 accommodating theplate-shaped opening and closing plate 90, the reducing effect of thestarting impact is noticeable in the same manner as the case of thefirst embodiment.

FIG. 20 shows a fixed displacement type piston compressor 10A inaccordance with an eleventh embodiment. The compressor 10A has aplurality of one headed pistons 95. The same reference numerals are usedin the same components as those of the first embodiment.

A whole housing of the compressor 10A is constituted by the cylinderblock 12, the front housing member 13, and the rear housing member 14.The swash plate 23 is accommodated in the swash plate chamber 24 definedbetween the cylinder block 12 and the front housing member 13. A oneheaded piston 95 linked to the swash plate 23 reciprocates within thecylinder bore 28 in accordance with the rotation of the swash plate 23.The rotary valve 36 is provided in the rotary shaft 21 so as tocorrespond to the cylinder block 12. The valve body 42 is provided inthe rear housing member 14 so as to define the working pressure chamber412.

The eleventh embodiment also has the same advantages as those of thefirst embodiment.

FIGS. 21 to 26 show a twelfth embodiment in accordance with the presentinvention.

As shown in FIG. 21, the in-shaft passage 31 is formed within the rotaryshaft 21 so as to be along the rotation axis 210 of the rotary shaft 21.The communication chamber 88 and the valve hole 891 are formed in therear housing member 14, and the plate-shaped opening and closing plate90 is accommodated within the communication chamber 88 in such a manneras to be capable of opening and closing the valve hole 891. The valvehole 891 extends through the partition wall 89 which separates thecommunication chamber 88 and the suction chamber 142. The inlet 311 ofthe in-shaft passage 31 is positioned in the end surface of the rotaryshaft 21 within the rear cylinder block 12, and is open to thecommunication chamber 88 within the rear housing member 14.

As shown in FIGS. 23 and 24, an electromagnetic solenoid 248, whichserves as an electromagnetic drive portion, is attached to the end wall40 of the rear housing member 14. The rear housing member 14 is made ofaluminum and forms the suction chamber 142. An installation recess 404is formed in a recessed manner in an outer surface of the end wall 40.The electromagnetic solenoid 248 includes a fixed iron core 250, amovable iron core 251, a second return spring 252, and a coil 253.

The fixed iron core 250 is fitted to the installation recess 404, and acoil 253 is embedded in the fixed iron core 250. The installation recess404 is connected to the suction chamber 142. A pressure recess 260,which serves as a pressure chamber forming recess, is formed in arecessed manner in the fixed iron core 250. The pressure recess 260 isopen toward the suction chamber 142. The movable iron core 251 isslidably fitted to the pressure recess 260. The movable iron core 251defines a pressure chamber 262 within the pressure recess 260. A groove254 is formed in a peripheral surface of the movable iron core 251. Thegroove 254 connects the pressure recess 260 with the suction chamber142. Accordingly, the pressure within the pressure chamber 262corresponds to the pressure within the suction chamber 142. The pressureof the suction chamber 142, that is, the suction pressure acts against apressure in the pressure chamber 262 via the movable iron core 251. Alid 258 fastened to the outer surface of the end wall 40 retains thefixed iron core 250 and the coil 253 within the installation recess 404.

The movable iron core 251 has an attaching hole 255, which serves as athrough hole. The attaching hole 255 extends through the movable ironcore 251 in such a manner as to be connected to the suction chamber 142from the pressure recess 260. The transmission rod 92 is press fitted tothe attaching hole 255 from an opening of the attaching hole 255 facingthe suction chamber 142, and is fixed thereto. The opening and closingplate 90 is fastened to a distal end of the transmission rod 92.

The movable iron core 251, the transmission rod 92 and the opening andclosing plate 90 construct the valve body 242 opening and closing thevalve hole 891. The valve body 242 defines the pressure chamber 262within the pressure recess 260.

The second return spring 252 is arranged between the transmission rod 92and a bottom 261 of the pressure recess 260. The second return spring252 urges the transmission rod 92 in a direction in which the secondreturn spring 252 moves the transmission rod 92 away from the bottom261. In other words, the movable iron core 251 is urged in a directionin which the movable iron core 251 pops out of the pressure recess 260toward the suction chamber 142, on the basis of the spring force of thesecond return spring 252. The electromagnetic solenoid 248, the valvebody 242 and the second return spring 252 construct a switch portion.The switch portion is capable of switching the suction chamber 142,which serves as a portion of the suction pressure zone within thecompressor 10, to a communication state, in which the suction chamber142 communicates with the front outlet 312 and the rear outlet 313 ofthe in-shaft passage 31, and a shutoff state, in which the suctionchamber 142 is shut off from the front outlet 312 and the rear outlet313.

In FIG. 23, the valve body 242 is located in the communication position,at which the valve body 242 connects the communication chamber 88 withthe suction chamber 142, by opening the valve hole 891. In FIG. 24, thevalve body 242 is located at the shutoff position at which the valvebody 242 shuts off the communication chamber 88 from the suction chamber142 by closing the valve hole 891. The second return spring 252 urgesthe valve body 242 from the shutoff position toward the communicationposition. In other words, the switch portion is capable of switching thesuction chamber 142 to a communication state [a state shown in FIG. 23],in which the suction chamber 142 communicates with the front outlet 312and the rear outlet 313 of the in-shaft passage 31, and a shutoff state[a state shown in FIG. 24], in which the suction chamber 142 is shut offfrom the front outlet 312 and the rear outlet 313 of the in-shaftpassage 31.

If the electric current is fed to the coil 253, the fixed iron core 250attracts the movable iron core 251 against a spring force of the secondreturn spring 252. In other words, an electromagnetic force generated byexciting the coil 253 drives the valve body 242 from the communicationposition toward the shutoff position. The electromagnetic solenoid 248can be switched to a first state, in which the electromagnetic solenoid248 arranges the valve body 242 at the communication position by beingdemagnetized, and a second state, in which the electromagnetic solenoid248 arranges the valve body 242 at the shutoff position by beingmagnetized.

The magnetizing and demagnetizing of the electromagnetic solenoid 248and the electromagnetic clutch 25 are controlled by the control computerC.

A valve waveform W in a timing chart in FIG. 26 shows a current feedingtiming with respect to the electromagnetic solenoid 248. A firstexciting period section V1 in the valve waveform W is set incorrespondence to a clutch starting time t1. A starting time t3 of thefirst exciting period section V1 is before the clutch starting time t1,and an ending time t4 of the first exciting period section V1 is afterthe clutch starting time t1. In other words, the control computer Cfirst carries out the current feed to the electromagnetic solenoid 248and thereafter carries out the current feed to the electromagneticclutch 25, at a time of starting the current feed to the electromagneticclutch 25.

FIG. 25 is a flowchart showing an operation control program forcontrolling the operation of the compressor 10, and the control computerC controls the operation of the compressor 10 on the basis of theoperation control program shown by the flowchart. A description will begiven below of the operation control of the compressor 10 in accordancewith the operation control program shown by the flowchart. FIG. 25 hassteps S1 to S7 and S18. Steps S1 to S7 are the same as the case of FIG.5 except the matter that the electromagnetic three-way valve 48 isreplaced by the electromagnetic solenoid 248.

If the compressor 10 is in the operation stop state, and theelectromagnetic solenoid 248 is in the demagnetized state, the valvebody 242 is arranged at the communication position shown in FIG. 23 onthe basis of the spring force of the second return spring 252.

As shown in FIG. 23, in the case of YES in step S1, that is, in the caseof the compressor operation starting mode, the control computer C startsthe current application to the electromagnetic solenoid 248 in step S2.If the electric current is fed to the electromagnetic solenoid 248, thevalve body 242 is arranged at the shutoff position shown in FIG. 24against the spring force of the second return spring 252, and the valvehole 891 is closed. Accordingly, the suction chamber 142 is shut offfrom the communication chamber 88.

In the case of YES in step S3, that is, in the case that a period ta haselapsed after starting the current application to the electromagneticsolenoid 248, the control computer C starts the current application tothe electromagnetic clutch 25 in step S4. Accordingly, theelectromagnetic clutch 25 gives way to the coupled state from theshutoff state, and the rotary shaft 21 and the swash plate 23 startrotating.

In the case of YES in step S5, that is, in the case that a period tb haselapsed after starting the current application to the electromagneticclutch 25, the control computer C stops the current application to theelectromagnetic solenoid 248 in step S6. If the current feed to theelectromagnetic solenoid 248 is stopped, the valve body 242 is arrangedat the communication position shown in FIG. 23 from the shutoff positionshown in FIG. 24, on the basis of the spring force of the second returnspring 252. Accordingly, the valve hole 891 is opened, and thecommunication chamber 88 communicates with the suction chamber 142.Therefore, the refrigerant within the suction chamber 142 flows in thein-shaft passage 31 via the valve hole 891 and the communication chamber88.

After stopping the current application to the electromagnetic solenoid248, the control computer C determines in step S7 whether the compressoroperation stopping mode is established, on the basis of the comparisonbetween the detected temperature and the target temperature. In the caseof YES in step S7, that is, in the case of the compressor operationstopping mode, the control computer C stops the current application tothe electromagnetic clutch 25 in step S18. After the process of stepS18, the control computer C gives way to step S1.

The torque waveform T1 in FIG. 26 is one example of the torquefluctuation. In the case that the current application to theelectromagnetic clutch 25 is started, the torque is fluctuated. However,at a time of starting the current application to the electromagneticclutch 25, it is possible to suppress a rapid torque fluctuation [afluctuation portion T11 in the torque waveform T1] in the case that thecurrent application to the electromagnetic clutch 25 is started, byexciting the electromagnetic solenoid 248 before starting the currentapplication to the electromagnetic clutch 25 and stopping the currentapplication to the electromagnetic solenoid 248 after starting thecurrent application to the electromagnetic clutch 25.

The twelfth embodiment has the following advantages.

(2-1) In the state in which the electromagnetic solenoid 248 ismagnetized, the valve body 242 is arranged at the shutoff position shownin FIG. 24. If the valve body 242 is arranged at the shutoff position,the suction chamber 142, which is the suction pressure zone within thecompressor 10, is shut off from the communication chamber 88.Accordingly, at a time when the operation of the compressor 10 isstarted, that is, at a time when the rotation of the rotary shaft 21 isstarted, the rotation of the rotary shaft 21 is started after the valvebody 242 is previously arranged at the shutoff position. Therefore, therefrigerant does not flow in the communication chamber 88 and thein-shaft passage 31 from the suction chamber 142. Accordingly, the rapidtorque fluctuation is suppressed and the starting impact is reduced.

(2-2) The opening and closing plate 90 for shutting off the suctionchamber 142 within the compressor 10 from the communication chamber 88is shaped like a plate. Accordingly, it is possible to reduce thevolumetric capacity of the communication chamber 88 accommodating theopening and closing plate 90. Therefore, the amount of the refrigerantcompressed by the front compression chamber 271 and the rear compressionchamber 281 is small at a time when the valve body 242 exists at theshutoff position. As a result, the effect of suppressing the torquefluctuation, that is, the effect of reducing the starting impact isnoticeable.

(2-3) If the electromagnetic solenoid 248 is demagnetized, the valvebody 242 is returned to the communication position on the basis of thespring force of the second return spring 252. The use of the secondreturn spring 252 simplifies the structure for returning the valve body242 to the communication position.

(2-4) If it is impossible to magnetize the electromagnetic solenoid 248,the valve body 242 is retained at the communication position on thebasis of the spring force of the second return spring 252 within thepressure chamber 262. Accordingly, if the compressor 10 starts beingoperated, the refrigerant within the suction chamber 142 flows in thefront compression chamber 271 and the rear compression chamber 281 viathe communication chamber 88 and the in-shaft passage 31. In otherwords, even in the case that it becomes impossible to magnetize theelectromagnetic solenoid 248, the cooling operation is carried outnormally.

(2-5) If the refrigerant leaks from the suction chamber 142 to thecommunication chamber 88 via the valve hole 891 at a time when the valvebody 242 closes the valve hole 891, the reducing effect of the startingimpact is lowered. However, in accordance with the present embodiment,the communication chamber 88 is securely shut off from the suctionchamber 142, in the state in which the flat seal surface 901 of theopening and closing plate 90 comes into surface contact with the flatvalve seat surface 892. Accordingly, it is possible to prevent therefrigerant from leaking from the suction chamber 142 to thecommunication chamber 88 via the valve hole 891, at a time when thevalve body 242 closes the valve hole 891.

FIG. 27 explains a thirteenth embodiment. The apparatus structure is thesame as the case of the twelfth embodiment.

In the thirteenth embodiment, the apparatus structure is the same as thecase of the twelfth embodiment, however, as shown by a currentapplication starting section K21 in a clutch waveform K2, the thirteenthembodiment is different from the case of the twelfth embodiment in apoint that the amount of current application at a time of starting thecurrent application to the electromagnetic clutch 25 is graduallyincreased. After the feed current value to the electromagnetic clutch 25becomes maximum, the current application to the electromagnetic solenoid248 is stopped. The fluctuation of the fluctuation portion T21 in thetorque waveform T2 expressing the torque fluctuation is suppressed incomparison with the case of the twelfth embodiment, on the basis of thestart of the current application to the electromagnetic clutch 25.

For example, in a conventional fixed displacement type piston compressorhaving no switch portion, the torque at a time of starting is great,that is, the load of the electromagnetic clutch 25 is great.Accordingly, if the amount of current application is gradually increasedin the same manner as the present embodiment, slip is generated in theelectromagnetic clutch 25. Accordingly, it is hard to ensure thereliability of the electromagnetic clutch 25.

In the present embodiment, the torque at a time of starting is small,that is, the load applied to the electromagnetic clutch 25 is small.Accordingly, it is possible to carry out such an operation control as togradually increase the amount of current application to theelectromagnetic clutch 25.

FIGS. 28A and 28B explain a fourteenth embodiment. The same referencenumerals are attached to the same component as the twelfth embodiment.

A valve body 242A is provided with the opening and closing plate 90, amovable iron core 251A, and a transmission rod 92. The movable iron core251A is slidably fitted to a pressure recess 260. The transmission rod92 is integrally formed in the movable iron core 251A. The movable ironcore 251A defines a pressure chamber 262 within the pressure recess 260.The first return spring 94 is arranged between the movable iron core251A and the partition wall 89. The first return spring 94 urges thevalve body 242A in a direction of pressing the movable iron core 251Ainto the pressure recess 260. If the electromagnetic solenoid 248 ismagnetized, an electromagnetic driving force of the electromagneticsolenoid 248 drives the valve body 242A in a direction of pressing themovable iron core 251A into the pressure recess 260. The first returnspring 94 serves as a retaining spring retaining the valve body 242A atthe shutoff position.

In FIG. 28A, the valve body 242A exists at the shutoff position at whichthe valve body 242A closes the valve hole 891, and in FIG. 28B, thevalve body 242A exists at the communication position at which the valvebody 242A opens the valve hole 891. In the case that the electromagneticsolenoid 248 is in the magnetized state, the valve body 242A exists atthe shutoff position shown in FIG. 28A on the basis of theelectromagnetic force of the electromagnetic solenoid 248. A timing atwhich the electromagnetic solenoid 248 is magnetized is the same as thecase of the twelfth embodiment. In the case that the operation of thecompressor 10 is in the stop state, the valve body 242A is retained atthe shutoff position shown in FIG. 28A on the basis of the spring forceof the first return spring 94.

If the electromagnetic solenoid 248 is magnetized before the compressor10 starts being operated, and the operation of the compressor 10 isstarted thereafter, the starting impact is reduced in the same manner asthe case of the twelfth embodiment because the valve body 242A exists atthe shutoff position.

If the electromagnetic solenoid 248 is demagnetized after starting theoperation of the compressor 10, the valve body 242A is released from theelectromagnetic force of the electromagnetic solenoid 248. Since therefrigerant within the in-shaft passage 31 and the refrigerant withinthe communication chamber 88 are drawn into the front compressionchamber 271 (refer to FIG. 21) and the rear compression chamber 281, adifference is generated between the pressure within the suction chamber142 and the pressure within the communication chamber 88. Accordingly,the opening and closing plate 90 separates from the valve seat surface892 against the spring force of the first return spring 94. If theopening and closing plate 90 separates from the valve seat surface 892,the refrigerant within the suction chamber 142 is drawn to thecommunication chamber 88 via the valve hole 891. Accordingly, thepressure within the suction chamber 142 becomes lower than the pressurewithin the pressure chamber 262. In other words, a difference isgenerated between the pressure within the suction chamber 142 and thepressure within the pressure chamber 262.

The spring force of the first return spring 94 is set to such amagnitude that the first return spring 94 is compressed by thedifferential pressure generated between the pressure within the suctionchamber 142 and the pressure within the pressure chamber 262 at a timeof operating the compressor 10. In other words, the spring force of thefirst return spring 94 is set such as to yield to the differentialpressure mentioned above. Accordingly, the differential pressuregenerated between the pressure within the suction chamber 142 and thepressure within the pressure chamber 262 at a time of operating thecompressor 10 overcomes the spring force of the first return spring 94and retains the valve body 242A at the communication position shown inFIG. 28B.

The fourteenth embodiment has the same advantages as the items (2-1) and(2-4) in the twelfth embodiment. If the electromagnetic solenoid 248 ismagnetized, it is possible to securely retain the valve body 242A at theshutoff position. If the electromagnetic solenoid 248 is in thedemagnetized state by appropriately setting the spring force of thefirst return spring 94, the valve body 242A is arranged at thecommunication position in the case that the compressor 10 is operated,and the cooling operation is securely carried out.

FIGS. 29A and 29B explain a fifteenth embodiment. The same referencenumerals are used in the same components as those of the twelfthembodiment.

A spool-shaped valve body 342 is slidably fitted into a pressure recess611 which is the cylinder interior of the cylinder 41, in the end wall40 of the rear housing member 14. The valve body 342 is provided withthe disc-shaped piston portion 43, the cylinder portion 44 and a movableiron core portion 345. A cylinder interior 442 is an internal passage ofthe valve body 342. The piston portion 43 defines a pressure chamber 612within the pressure recess 611.

A groove 443 is formed in an outer peripheral surface of the cylinderportion 44 in such a manner that the groove 443 connects the suctionchamber 142 with the pressure chamber 612. A pressure in the pressurechamber 612 corresponds to a pressure in the suction chamber 142, andthe pressure (the suction pressure) in the suction chamber 142 actsagainst the pressure in the pressure chamber 612 via the valve body 342.

A fitting hole 403 extends through the end wall 40, and an accommodationcylinder 346 is fitted to the fitting hole 403. A fixed iron core 364 isaccommodated within the accommodation cylinder 346. The movable ironcore portion 345 is fitted into the accommodation cylinder 346 in such amanner as to face the fixed iron core 364. A coil 365 is arranged in anouter peripheral surface of the accommodation cylinder 346. If the coil365 is excited, the movable iron core portion 345 is attracted to thefixed iron core 364. The fixed iron core 364, the movable iron coreportion 345 and the coil 365 construct an electromagnetic solenoid 347,which serves as an electromagnetic driving portion.

The guide cylinder 45 surrounds the rotation axis 210. If the valve body342 comes close to the end wall 40, the volumetric capacity of thepressure chamber 612 is reduced. The electromagnetic solenoid 347, thevalve body 342 and the first return spring 47 construct the switchportion. The switch portion is capable of switching the suction chamber142, which is a portion of the suction pressure zone within thecompressor 10, to the communication state, in which the suction chamber142 communicates with the front outlet 312 and the rear outlet 313 ofthe in-shaft passage 31, and the shutoff state, in which the suctionchamber 142 is shut off from the front outlet 312 and the rear outlet313. The first return spring 47 serves as the retaining spring retainingthe valve body 342 at the shutoff position.

In the state shown in FIG. 29B, a whole of the introduction port 441 islocated at a position exposed to the interior of the suction chamber142, and the in-shaft passage 31 communicates with the suction chamber142 via the cylinder interior 451 of the guide cylinder 45, the cylinderinterior 442 of the cylinder portion 44 and the introduction port 441.In the state shown in FIG. 29A, the introduction port 441 is located ata position at which the entire introduction port 441 enters the pressurerecess 611, and the in-shaft passage 31 is shut off from the suctionchamber 142. FIG. 29B shows a state in which the valve body 342 is in astate of being at the communication position connects the in-shaftpassage 31 and the suction chamber 142, and FIG. 29A shows a state inwhich the valve body 342 is in a state of being at the shutoff position,at which the valve body 342 shuts off the in-shaft passage 31 and thesuction chamber 142.

In the case that the electromagnetic solenoid 347 is in the magnetizedstate, the valve body 342 exists at the shutoff position shown in FIG.29A on the basis of the electromagnetic force of the electromagneticsolenoid 347. The timing at which the electromagnetic solenoid 347 ismagnetized is the same as the case of the twelfth embodiment. In thecase that the operation of the compressor 10 is in the stop state, thevalve body 342 is retained at the shutoff position shown in FIG. 29A onthe basis of the spring force of the first return spring 47. In otherwords, the switch portion is capable of switching the suction chamber142 to the communication state [the state shown in FIG. 29B] in whichthe suction chamber 142 communicates with the front outlet 312 and therear outlet 313 of the in-shaft passage 31, and the shutoff state [thestate shown in FIG. 29A] in which the suction chamber 142 is shut offfrom the front outlet 312 and the rear outlet 313 of the in-shaftpassage 31.

If the electromagnetic solenoid 347 is magnetized before the compressor10 starts being operated, and the operation of the compressor 10 isstarted thereafter, the starting impact is reduced in the same manner asthe case of the twelfth embodiment because the valve body 342 exists atthe shutoff position.

If the electromagnetic solenoid 347 is demagnetized after starting theoperation of the compressor 10, the valve body 342 is released from theelectromagnetic force of the electromagnetic solenoid 347. Since therefrigerant within the cylinder interior 451 and the in-shaft passage 31is drawn to the front compression chamber 271 (refer to FIG. 21) and therear compression chamber 281, a difference is generated between thepressure in the suction chamber 142 and the pressure in the pressurechamber 612, on the basis of the drawing operation. The spring force ofthe first return spring 47 is set to such a magnitude that the firstreturn spring 47 is compressed by the differential pressure generatedbetween the pressure within the suction chamber 142 and the pressurewithin the pressure chamber 612 at a time of operating the compressor10. Accordingly, the differential pressure generated between thepressure in the suction chamber 142 and the pressure in the pressurechamber 612 at a time of operating the compressor 10 overcomes thespring force of the first return spring 47, and retains the valve body342 at the communication position shown in FIG. 29B.

The fifteenth embodiment has the same advantages as those of the twelfthembodiment.

FIGS. 30A and 30B explain a sixteenth embodiment. The same referencenumerals are used in the same components as those of the fifteenthembodiment.

The guide cylinder 45A fitted to the cylinder portion 44 of the valvebody 342 is formed as a closed-end cylindrical shape, and is formedindependently from the rear cylinder block 12, the rotary shaft 21 andthe like. The bottom wall of the guide cylinder 45A comes into contactwith the end surface 122 of the rear cylinder block 12, and the guidecylinder 45A is fitted to the cylinder portion 44 of the valve body 342in such a manner as to be allowed to move in the radial direction of therotary shaft 21 with respect to the rotary shaft 21. The communicationport 452 is formed in the bottom wall of the guide cylinder 45A in sucha manner as to connect the cylinder interior 451 of the guide cylinder45A with the in-shaft passage 31, and the first return spring 47 isarranged between the bottom wall of the guide cylinder 45A and thepiston portion 43. In FIG. 30A, the valve body 342 is arranged at theshutoff position, and the valve body 342 is arranged at thecommunication position in FIG. 30B.

On the assumption that the refrigerant leaks through a clearance betweenthe valve body 342 and the cylinder 41 or a clearance between the valvebody 342 and the guide cylinder 45A at a time when the valve body 342exists at the shutoff position, the effect of reducing the startingimpact is lowered.

However, in the present embodiment, the guide cylinder 45A is fitted tothe cylinder portion 44 of the valve body 342 in such a manner that theguide cylinder 45A is allowed to move in the radial direction of therotary shaft 21 with respect to the rotary shaft 21. Accordingly, theaxis 413 of the pressure recess 611 is allowed to come into line withthe axis 453 of the guide cylinder 45A. Therefore, it is possible toreduce the clearance between the cylinder portion 44 of the valve body342 and the cylinder 41 and the clearance between the cylinder portion44 of the valve body 342 and the guide cylinder 45A, and it is possibleto prevent the refrigerant from leaking along the peripheral surface ofthe cylinder portion 44 of the valve body 342.

FIGS. 31A and 31B explain a seventeenth embodiment. The same referencenumerals are used in the same components as those of the fifteenthembodiment.

The piston 69 is slidably fitted to the cylinder 41, and the movableiron core portion 345 is integrally formed in the piston 69. The piston69 defines the pressure chamber 612 within the pressure recess 611. Thetransmission rod 70 is coupled to the piston 69.

The small circumferential surface body 71, the large circumferentialsurface body 72, the transmission rod 70 and the piston 69 construct thevalve body defining the pressure chamber 612 within the pressure recess611.

FIG. 31A shows a state in which the small circumferential surface body71 closes the front outlet 312, and the large circumferential surfacebody 72 closes the rear outlet 313, and the front outlet 312 and therear outlet 313 are shut off from the in-shaft passage 31A. FIG. 31Bshows a state in which the small circumferential surface body 71 opensthe front outlet 312, and the large circumferential surface body 72opens the rear outlet 313, and the front outlet 312 and the rear outlet313 communicate with the in-shaft passage 31A. If the electromagneticsolenoid 347 is excited, the small circumferential surface body 71 andthe large circumferential surface body 72 are arranged at the shutoffposition shown in FIG. 31A from the communication position shown in FIG.31B on the basis of the spring force of the first return spring 73. Thefirst return spring 73 serves as the retaining spring retaining thesmall circumferential surface body 71 and the large circumferentialsurface body 72 at the shutoff position.

The seventeenth embodiment has the same advantages as those of thetwelfth embodiment. Further, in the seventeenth embodiment, since therefrigerant which can flow in the front compression chamber 271 and therear compression chamber 281 at a time when the small circumferentialsurface body 71 and the large circumferential surface body 72 exist atthe shutoff position is constituted only by the refrigerant within thefront outlet 312 and the rear outlet 313, and within the frontcommunication passage 32 and the rear communication passage 33, theeffect of reducing the starting impact is more noticeable than the caseof the twelfth embodiment.

Further, if the piston 69 is structured such as to be relativelyrotatable with respect to the transmission rod 70, it is possible toprevent the first return spring 73 from relatively rotating with respectto the rotary shaft 21. Accordingly, it is possible to avoid theabrasion and damage of the first return spring 73 or the rotary shaft 21caused by the relative rotation between the first return spring 73 andthe rotary shaft 21. Alternatively, the large circumferential surfacebody 72 may be structured such as to be relatively rotatable withrespect to the first return spring 73.

FIGS. 32A and 32B explain an eighteenth embodiment. The same referencenumerals are used in the same components as those of the seventeenthembodiment.

As shown in FIG. 32A, in the case that the large circumferential surfacebody 72 is located at the position at which it closes the rear outlet313, the circular plate 74 exists at an upstream side of the frontoutlet 312 within the in-shaft passage 31A. Accordingly, the refrigerantin the in-shaft passage 31A cannot flow in the front compression chamber271 via the front outlet 312. As shown in FIG. 32B, in the case that thelarge circumferential surface body 72 is located at the position atwhich it opens the rear outlet 313, the circular plate 74 exists in adownstream side of the front outlet 312 within the in-shaft passage 31A.Accordingly, the refrigerant in the in-shaft passage 31A can flow in thefront compression chamber 271 via the front outlet 312. If theelectromagnetic solenoid 347 is excited, the cylinder 75 is arranged atthe shutoff position shown in FIG. 32A from the communication positionshown in FIG. 32B, on the basis of the spring force of the first returnspring 73. The circular plate 74, the large circumferential surface body72, the transmission rod 70, and the piston 69 construct a valve bodywhich defines the pressure chamber 612 within the pressure recess 611.

The eighteenth embodiment has the same advantages as those of theseventeenth embodiment.

FIGS. 33A and 33B explain a nineteenth embodiment. The same referencenumerals are used in the same components as those of the seventeenthembodiment.

The cylinder 75 can slide within the in-shaft passage 31A in a state inwhich the angular pin 76 is inserted to an end wall 752 of the cylinder75. The cylinder 75 and the piston 69 construct a valve body whichdefines the pressure chamber 612 within the pressure recess 611.

FIG. 33B shows a state in which the small-diameter cylindrical portion77 closes the front outlet 312, and shows a state in which thelarge-diameter cylindrical portion 78 closes the rear outlet 313.Accordingly, the front outlet 312 and the outlet 313 are shut off fromthe cylinder interior 750 of the cylinder 75. FIG. 33A shows a state inwhich the communication port 771 of the small-diameter cylindricalportion 77 communicates with the front outlet 312, and shows a state inwhich the communication port 781 of the large-diameter cylindricalportion 78 communicates with the rear outlet 313, and the front outlet312 and the rear outlet 313 communicate with the cylinder interior 750.If the electromagnetic solenoid 347 is excited, the cylinder 75 isarranged at the shutoff position shown in FIG. 33B from thecommunication position shown in FIG. 33A, on the basis of the springforce of the first return spring 73.

The nineteenth embodiment has the same advantages as those of theseventeenth embodiment.

FIG. 34 shows a compressor 10A having one headed pistons 95 inaccordance with a twentieth embodiment. The electromagnetic solenoid 248and the valve body 242 are provided in the rear housing member 14. Thetwentieth embodiment has the same advantages as those of the twelfthembodiment.

The embodiments mentioned above may be modified as follows.

In FIGS. 3 and 4, the discharge refrigerant fed to the working pressurechamber 412 may be taken from a portion of the external refrigerantcircuit in the upstream side of the heat exchanger 37.

The electromagnetic three-way valve 48 shown in FIGS. 12 and 13 may beincorporated by being coupled to the rear housing member 14.

The electromagnetic on-off valve 67 in FIGS. 8 to 9A may be incorporatedin the rear housing member 14. Further, the electromagnetic on-off valve67A in FIGS. 10 to 11A may be incorporated in the rear housing member14.

The check valve 68 in FIGS. 8 to 11A may be incorporated in the housingof the compressor 10.

The oil separator 79 in FIGS. 17 to 18B may be incorporated in thehousing of the compressor 10.

The valve body 42 may be arranged at the communication position in thecase of magnetizing the electromagnetic three-way valve 48 in FIGS. 3and 4, and the valve body 42 may be arranged at the shutoff position inthe case of demagnetizing the electromagnetic three-way valve 48.

The valve body 242 may be arranged at the communication position in thecase of magnetizing the electromagnetic solenoid 248 in FIGS. 23 and 24,and the valve body 242 may be arranged at the shutoff position in thecase of demagnetizing the electromagnetic solenoid 248.

The valve body 342 may be arranged at the communication position in thecase of magnetizing the electromagnetic solenoid 347 in FIGS. 29A and29B, and the valve body 342 may be arranged at the shutoff position inthe case of demagnetizing the electromagnetic solenoid 347.

The pressure chamber 262 in FIGS. 23 and 24 may be always shut off fromthe suction chamber 142, and the pressure chamber 262 may communicatewith the atmospheric air.

Each of the first rotary valve 35 and the second rotary valve 36 may beformed independently from the rotary shaft 21.

1. A refrigerant suction structure in a fixed displacement type pistoncompressor, wherein the compressor comprises: a rotary shaft coupled toan external drive source via a clutch; a plurality of cylinder boresarranged around the rotary shaft; a plurality of pistons definingcompression chambers in the cylinder bores by being respectivelyaccommodated in the cylinder bores; a cam body integrated with therotary shaft, the cam body converting a rotation of the rotary shaftinto reciprocation of each of the pistons; a suction pressure zone; anda rotary valve having an introduction passage for introducing arefrigerant from the suction pressure zone to each of the compressionchambers, the rotary valve integrally rotating with the rotary shaft,the suction pressure zone having a portion within the compressor, andthe introduction passage having outlets for feeding out the refrigeranttoward each of the compression chambers, wherein the refrigerant suctionstructure has a switch portion capable of being switched between acommunication state and a shutoff state, wherein the switch portion inthe communication state allows the portion of the suction pressure zonewithin the compressor to communicate with the outlets of theintroduction passage, wherein the switch portion in the shutoff stateshuts off the portion of the suction pressure zone within the compressorfrom the outlets of the introduction passage, wherein the switch portionincludes: a valve body capable of being switched between a communicationposition and a shutoff position, the valve body in the communicationposition allowing the portion of the suction pressure zone within thecompressor to communicate with the outlets of the introduction passage,and the valve body in the shutoff position shutting off the portion ofthe suction pressure zone within the compressor from the outlets of theintroduction passage; a working pressure chamber introducing a workingpressure that is applied to the valve body so as to arrange the valvebody at the communication position; and a working pressure applyingportion applying the working pressure to the working pressure chamber,and wherein the pressure in the suction pressure zone acts against thepressure in the working pressure chamber through the valve body.
 2. Therefrigerant suction structure according to claim 1, wherein the switchportion has a working pressure recess, and the valve body is slidablyfitted into the working pressure recess, whereby the valve body definesthe working pressure chamber within the working pressure recess, whereinthe pressure of the portion of the suction pressure zone within thecompressor acts against the pressure of the working pressure chamber viathe valve body, and wherein the switch portion is provided with a firstreturn spring for returning the valve body to the shutoff position fromthe communication position.
 3. The refrigerant suction structureaccording to claim 2, wherein the introduction passage has an inlet foraccepting the refrigerant from the suction pressure zone, and wherein,in the case that the switch portion is in the shutoff state, the valvebody is arranged in such a manner as to shut off the inlet of theintroduction passage from the portion of the suction pressure zonewithin the compressor.
 4. The refrigerant suction structure according toclaim 3, wherein the inlet of the introduction passage is positioned inan end surface of the rotary valve, and the outlets of the introductionpassage are positioned in a peripheral surface of the rotary valve,wherein a rotation axis of the rotary valve intersects the end surface,wherein the refrigerant suction structure comprises: a valveaccommodation chamber rotatably accommodating the rotary valve; and aguide cylinder surrounding the rotation axis outside the valveaccommodation chamber, wherein a cylinder interior of the guide cylindercommunicates with an inlet of the introduction passage, wherein thevalve body is slidably fitted to the guide cylinder, the valve body hasan internal passage communicating with the cylinder interior of theguide cylinder, and the internal passage has an inlet for accepting therefrigerant from the suction pressure zone, wherein, in the case thatthe valve body exists at the shutoff position, the inlet of the internalpassage is shut off by entering the working pressure recess, andwherein, in the case that the valve body exists at the communicationposition, the inlet of the internal passage is positioned outside theworking pressure recess, so that the inlet is exposed to the interior ofthe portion of the suction pressure zone within the compressor.
 5. Therefrigerant suction structure according to claim 4, wherein the guidecylinder is formed as an independent body from members of the compressorother than the valve body, so as to be allowed to move in a radialdirection of the rotary shaft with respect to members of the compressorother than the valve body.
 6. The refrigerant suction structureaccording to claim 2, wherein the introduction passage has an inlet foraccepting the refrigerant from the suction pressure zone, and the inletof the introduction passage is positioned in an end surface of therotary valve, wherein the outlets of the introduction passage arepositioned in a peripheral surface of the rotary valve, wherein thevalve body is fitted into the introduction passage from the inlet of theintroduction passage, and wherein, in the case that the switch portionis in the shutoff state, the valve body is arranged in the introductionpassage in such a manner as to shut off the outlets of the introductionpassage from the portion of the suction pressure zone within thecompressor.
 7. The refrigerant suction structure according to claim 6,wherein the introduction passage has an in-shaft passage positioned inthe rotary shaft, and the in-shaft passage extends in a direction of arotation axis of the rotary shaft, wherein the outlets of theintroduction passage extend through a peripheral surface of the rotaryshaft so as to communicate with the in-shaft passage, wherein the valvebody is fitted into the in-shaft passage in such a manner as to beslidable in a direction of the rotation axis within the introductionpassage, wherein the valve body is moved in the direction of therotation axis within the in-shaft passage, so as to be switched betweenthe communication position and the shutoff position, and wherein thevalve body at the shutoff position shuts off the outlets of theintroduction passage with respect to the in-shaft passage.
 8. Therefrigerant suction structure according to claim 3, wherein the switchportion has a flat valve seat surface, the valve body has a flat sealsurface, and the seal surface comes into surface contact with the valveseat surface in a state in which the valve body exists at the shutoffposition.
 9. The refrigerant suction structure according to claim 1,wherein the compressor has a discharge pressure zone, wherein theworking pressure applying portion has an inflow passage reaching theworking pressure chamber from the discharge pressure zone, and whereinthe refrigerant in the discharge pressure zone is introduced to theworking pressure chamber via the inflow passage.
 10. The refrigerantsuction structure according to claim 9, wherein an oil separator isprovided on the inflow passage, and the oil separator separates oil fromthe refrigerant within the discharge pressure zone, wherein aconstriction is provided in a portion of the inflow passage in adownstream side of the oil separator, and wherein the portion of theinflow passage in the downstream side of the oil separator serves as anoil passage introducing the oil separated by the oil separator to theconstriction.
 11. The refrigerant suction structure according to claim9, wherein the discharge pressure zone has a portion within thecompressor, wherein the portion of the discharge pressure zone withinthe compressor is connected to the portion of the suction pressure zonewithin the compressor via an external refrigerant circuit, and theexternal refrigerant circuit has a portion of the discharge pressurezone, wherein the inflow passage is connected to the portion of thedischarge pressure zone of the external refrigerant circuit, wherein theworking pressure applying portion is provided with an electromagneticon-off valve for opening and closing the inflow passage, and a checkvalve, and wherein the check valve is arranged in a portion of theexternal refrigerant circuit in a downstream side of a connectionportion between the portion of the discharge pressure zone in theexternal refrigerant circuit and the inflow passage.
 12. The refrigerantsuction structure according to claim 1, wherein the working pressureapplying portion is provided with an electromagnetic three-way valve,wherein the working pressure chamber is connected to the electromagneticthree-way valve via a common passage, wherein the electromagneticthree-way valve is connected to a discharge pressure zone via a feedpassage, wherein the electromagnetic three-way valve is connected to asuction pressure zone via a discharge passage, and wherein theelectromagnetic three-way valve is structured to be switched between afirst state, in which the common passage communicates with the feedpassage, and a second state, in which the common passage communicateswith the discharge passage.
 13. The refrigerant suction structureaccording to claim 1, wherein the compressor comprises: a cylinder blockhaving the cylinder bores; and a rear housing member coupled to thecylinder block, and wherein the rear housing member has in it a suctionchamber, and the working pressure chamber is defined within the rearhousing member.
 14. A refrigerant suction structure in a fixeddisplacement type piston compressor, wherein the compressor comprises: arotary shaft coupled to an external drive source via a clutch; aplurality of cylinder bores arranged around the rotary shaft; aplurality of pistons defining compression chambers in the cylinder boresby being respectively accommodated in the cylinder bores; a cam bodyintegrated with the rotary shaft, the cam body converting a rotation ofthe rotary shaft into reciprocation of each of the pistons; a suctionpressure zone; and a rotary valve having an introduction passage forintroducing a refrigerant from the suction pressure zone to each of thecompression chambers, the rotary valve integrally rotating with therotary shaft, the suction pressure zone having a portion within thecompressor, and the introduction passage having outlets for feeding outthe refrigerant toward each of the compression chambers, wherein therefrigerant suction structure has a switch portion capable of beingswitched between a communication state and a shutoff state, wherein theswitch portion in the communication state allows the portion of thesuction pressure zone within the compressor to communicate with theoutlets of the introduction passage, wherein the switch portion in theshutoff state shuts off the portion of the suction pressure zone withinthe compressor from the outlets of the introduction passage, wherein theswitch portion includes: a valve body capable of being switched betweena communication position and a shutoff position, the valve body in thecommunication position allowing the portion of the suction pressure zonewithin the compressor to communicate with the outlets of theintroduction passage, and the valve body in the shutoff positionshutting off the portion of the suction pressure zone within thecompressor from the outlets of the introduction passage; and anelectromagnetic driving portion driving the valve body on the basis ofan electromagnetic force.
 15. The refrigerant suction structureaccording to claim 14, wherein the switch portion is provided with asecond return spring returning the valve body to the communicationposition, and wherein the electromagnetic driving portion drives thevalve body from the communication position toward the shutoff position.16. The refrigerant suction structure according to claim 15, wherein theswitch portion has a pressure recess, and the valve body is slidablyaccommodated within the pressure recess, whereby the valve body definesa pressure chamber within the pressure recess, wherein the pressurechamber communicates with the portion of the suction pressure zonewithin the compressor, wherein the pressure in the portion of thesuction pressure zone within the compressor acts against the pressure inthe pressure chamber via the valve body, wherein the second returnspring is accommodated in the pressure chamber, and the second returnspring urges the valve body in a direction in which the valve body popsout from the interior of the pressure recess, and wherein theelectromagnetic driving portion drives the valve body in such a manneras to push the valve body into the pressure recess.
 17. The refrigerantsuction structure according to claim 14, wherein the switch portion hasa pressure recess, and the valve body is slidably accommodated withinthe pressure recess, whereby the valve body defines a pressure chamberwithin the pressure recess, wherein the pressure chamber communicateswith the portion of the suction pressure zone within the compressor,wherein the pressure in the portion of the suction pressure zone withinthe compressor acts against the pressure in the pressure chamber via thevalve body, wherein the switch portion is provided with a retainingspring which acts to retain the valve body at the shutoff position bypressing the valve body into the pressure recess, and wherein theelectromagnetic driving portion drives the valve body from thecommunication position toward the shutoff position.
 18. The refrigerantsuction structure according to claim 17, wherein the introductionpassage has an inlet for accepting the refrigerant from the suctionpressure zone, and wherein, in the case that the switch portion is inthe shutoff state, the valve body is arranged in such a manner as toshut off the inlet of the introduction passage from the portion of thesuction pressure zone within the compressor.
 19. The refrigerant suctionstructure according to claim 18, wherein the switch portion has a flatvalve seat surface, the valve body has a flat seal surface, and the sealsurface comes into surface contact with the valve seat surface in astate in which the valve body exists at the shutoff position.
 20. Therefrigerant suction structure according to claim 17, wherein theintroduction passage has an inlet for accepting the refrigerant from thesuction pressure zone, and the inlet of the introduction passage ispositioned in an end surface of the rotary valve, wherein the outlets ofthe introduction passage are positioned in a peripheral surface of therotary valve, wherein a rotation axis of the rotary valve intersects theend surface, wherein the refrigerant suction structure comprises: avalve accommodation chamber rotatably accommodating the rotary valve;and a guide cylinder surrounding the rotation axis outside the valveaccommodation chamber, wherein a cylinder interior of the guide cylindercommunicates with an inlet of the introduction passage, wherein thevalve body is slidably fitted to the guide cylinder, the valve body hasan internal passage communicating with the cylinder interior of theguide cylinder, and the internal passage has an inlet for accepting therefrigerant from the suction pressure zone, wherein, in the case thatthe valve body exists at the shutoff position, the inlet of the internalpassage is shut off by entering the pressure recess, and wherein, in thecase that the valve body exists at the communication position, the inletof the internal passage is positioned outside of the pressure recess, sothat the inlet is exposed to the portion of the suction pressure zonewithin the compressor.
 21. The refrigerant suction structure accordingto claim 20, wherein the guide cylinder is formed as an independent bodyfrom members of the compressor other than the valve body, so as to beallowed to move in a radial direction of the rotary shaft with respectto the members of the compressor other than the valve body.
 22. Therefrigerant suction structure according to claim 14, wherein theintroduction passage has an inlet for accepting the refrigerant from thesuction pressure zone, and the inlet of the introduction passage ispositioned in an end surface of the rotary valve, wherein the outlets ofthe introduction passage are positioned in a peripheral surface of therotary valve, wherein the valve body is fitted into the introductionpassage from the inlet of the introduction passage, and wherein, in thecase that the switch portion is in the shutoff state, the valve body isarranged in the introduction passage in such a manner as to shut off theoutlets of the introduction passage from the portion of the suctionpressure zone within the compressor.
 23. The refrigerant suctionstructure according to claim 22, wherein the introduction passage has anin-shaft passage positioned in the rotary shaft, and the in-shaftpassage extends in a direction of a rotation axis of the rotary shaft,wherein the outlets of the introduction passage extends through aperipheral surface of the rotary shaft so as to communicate with thein-shaft passage, wherein the valve body is fitted into the in-shaftpassage in such a manner as to be slidable in a direction of therotation axis within the introduction passage, wherein the valve body ismoved in the direction of the rotation axis within the in-shaft passage,so as to be switched between the communication position and the shutoffposition, and wherein the valve body at the shutoff position shuts offthe outlets of the introduction passage with respect to the in-shaftpassage.
 24. The refrigerant suction structure according to claim 14,wherein the compressor comprises: a cylinder block having the cylinderbores; and a rear housing member coupled to the cylinder block, andwherein the rear housing member has in it a suction chamber, and thevalve body is arranged within the rear housing member.
 25. An operationcontrol method in a fixed displacement type piston compressor, whereinthe compressor comprises: a rotary shaft coupled to an external drivesource via a clutch; a plurality of cylinder bores arranged around therotary shaft; a plurality of pistons defining compression chambers inthe cylinder bores by being respectively accommodated in the cylinderbores; a cam body integrated with the rotary shaft, the cam bodyconverting a rotation of the rotary shaft into reciprocation of each ofthe pistons; a suction pressure zone; a rotary valve having anintroduction passage for introducing a refrigerant from the suctionpressure zone to each of the compression chambers; and a dischargepressure zone, wherein the rotary valves integrally rotate with therotary shaft, wherein the suction pressure zone has a portion within thecompressor, wherein the introduction passage has outlets for feeding outthe refrigerant toward each of the compressors, wherein the operationcontrol method comprises: preparing a switch portion capable of beingswitched between a communication state and a shutoff state, wherein theswitch portion in the communication state allows the portion of thesuction pressure zone within the compressor to communicate with theoutlets of the introduction passage, the switch portion in the shutoffstate shuts off the portion of the suction pressure zone within thecompressor from the outlets of the introduction passage, the switchportion is provided with a valve body, a working pressure chamber, and aworking pressure applying portion, wherein the valve body is capablebeing switched between a communication position allowing the portion ofthe suction pressure zone within the compressor to communicate with theoutlet of the introduction passage, and a shutoff position shutting offthe portion of the suction pressure zone within the compressor from theoutlets of the introduction passage, wherein the working pressurechamber introduces a working pressure applied to the valve body toarrange the valve body at the communication position, wherein theworking pressure applying portion applies the working pressure to theworking pressure chamber, and wherein the working pressure applyingportion is provided with a switch valve that is switched between a firststate, in which the refrigerant in the discharge pressure zone can befed to the working pressure chamber and a second state, in which therefrigerant in the discharge pressure chamber cannot be fed to theworking pressure chamber; setting the clutch to a coupled state aftersetting the switch valve to the second state, at a time of switching theclutch from the shutoff state to the coupled state; and switching theswitch valve to the first state after setting the clutch to the coupledstate.
 26. The operation control method according to claim 25, whereinthe clutch is an electromagnetic clutch which, when magnetized, comes tothe coupled state coupling the rotary shaft to the external drivingsource, and wherein the operation control method comprises: graduallyincreasing an electric current fed to the electromagnetic clutch tomagnetize the electromagnetic clutch, at a time of switching theelectromagnetic clutch from a demagnetized state to a magnetized state;and switching the switch valve from the second state to the first stateafter a value of the electric current becomes maximum.
 27. An operationcontrol method in a fixed displacement type piston compressor, whereinthe compressor comprises: a rotary shaft coupled to an external drivesource via a clutch; a plurality of cylinder bores arranged around therotary shaft; a plurality of pistons defining compression chambers inthe cylinder bores by being respectively accommodated in the cylinderbores; a cam body integrated with the rotary shaft, the cam bodyconverting a rotation of the rotary shaft into reciprocation of each ofthe pistons; a suction pressure zone; a rotary valve having anintroduction passage for introducing a refrigerant from the suctionpressure zone to each of the compression chambers, the rotary valveintegrally rotating with the rotary shaft, the suction pressure zonehaving a portion within the compressor, and the introduction passagehaving outlets for feeding out the refrigerant toward each of thecompression chambers, wherein the operation control method comprises:preparing a switch portion capable of being switched between acommunication state and a shutoff state, wherein the switch portion inthe communication state allows the portion of the suction pressure zonewithin the compressor to communicate with the outlets of theintroduction passage, the switch portion in the shutoff state shuts offthe portion of the suction pressure zone within the compressor from theoutlets of the introduction passage, the switch portion is provided witha valve body and an electromagnetic driving portion, wherein the valvebody is capable being switched between a communication position allowingthe portion of the suction pressure zone within the compressor tocommunicate with the outlets of the introduction passage, and a shutoffposition shutting off the portion of the suction pressure zone withinthe compressor from the outlets of the introduction passage, wherein theelectromagnetic driving portion is capable of driving the valve body onthe basis of an electromagnetic force, and the electromagnetic drivingportion is capable of switching the valve body between a first state, inwhich the valve body is arranged at the communication position, and asecond state, in which the valve body is arranged at the shutoffposition; wherein the operation control method comprises: setting theclutch to the coupled state after setting the electromagnetic drivingportion to the second state, at a time of switching the clutch from theshutoff state to the coupled state; and setting the electromagneticdriving portion to the first state after setting the clutch to thecoupled state.
 28. The operation control method according to claim 27,wherein the clutch is an electromagnetic clutch which, when magnetized,comes to the coupled state coupling the rotary shaft to the externaldriving source, and wherein the operation control method comprises:gradually increasing an electric current fed to the electromagneticclutch to magnetize the electromagnetic clutch, at a time of switchingthe electromagnetic clutch from a demagnetized state to a magnetizedstate; and demagnetizing the electromagnetic driving portion after avalue of the electric current becomes maximum.